Annual report pursuant to Section 13 and 15(d)

Schedule III-Real Estate and Accumulated Depreciation

v2.4.0.6
Schedule III-Real Estate and Accumulated Depreciation
 12 Months Ended
Dec. 31, 2011
Schedule III-Real Estate and Accumulated Depreciation  
Schedule III-Real Estate and Accumulated Depreciation

Corporate Office Properties Trust
Schedule III—Real Estate and Accumulated Depreciation
December 31, 2011
(Dollars in Thousands)

 
    
    
   Initial Cost    
   Gross Amounts Carried At Close of Period    
    
    
 
    
    
   Costs
Capitalized
Subsequent to
Acquisition 		   
    
    
Property (Type)(1)
  Location   Encumbrances(2)   Land   Building and
Land
Improvements 		  Land   Building and
Land
Improvements 		  Total(3)(4)   Accumulated
Depreciation(5) 		  Year
Built or
Renovated 		  Date
Acquired(6)

1000 Redstone Gateway (O)

   Huntsville, AL   $ 5,632   $ —   $ 14,142   $ —   $ —   $ 14,142   $ 14,142   $ —   (7)   3/23/10

10150 York Road (O)

   Hunt Valley, MD     —     2,700     11,623     5,564     2,700     17,187     19,887     (6,440 ) 1985   4/15/04

10270 Old Columbia Road (O)

   Columbia, MD     1,090     751     957     231     751     1,188     1,939     (208 ) 1988/2001   1/9/07

10280 Old Columbia Road (O)

   Columbia, MD     1,107     756     1,205     151     756     1,356     2,112     (162 ) 1988/2001   1/9/07

10290 Old Columbia Road (O)

   Columbia, MD     701     490     102     322     490     424     914     (174 ) 1988/2001   1/9/07

1055 North Newport Road (O)

   Colorado Springs, CO     —     972     9,523     —     972     9,523     10,495     (956 ) 2007 - 2008   5/19/06

10807 New Allegiance Drive (O)

   Colorado Springs, CO     —     1,840     14,924     71     1,840     14,995     16,835     (1,280 ) 2009   9/28/05

1099 Winterson Road (O)

   Linthicum, MD     12,012     1,323     5,293     2,281     1,323     7,574     8,897     (3,012 ) 1988   4/30/98

110 Thomas Johnson Drive (O)

   Frederick, MD     —     2,810     12,075     843     2,810     12,918     15,728     (2,142 ) 1987/1999   10/21/05

1101 Sentry Gateway (O)

   San Antonio, TX     —     1,178     10,269     —     1,178     10,269     11,447     (43 ) 2011   7/16/08

11311 McCormick Road (O)

   Hunt Valley, MD     —     2,308     21,310     7,132     2,308     28,442     30,750     (6,023 ) 1984/1994   12/22/05

114 National Business Parkway (O)

   Annapolis Junction, MD     —     364     3,109     9     364     3,118     3,482     (800 ) 2002   6/30/00

11751 Meadowville Lane (O)

   Richmond, VA     —     1,305     52,098     112     1,305     52,210     53,515     (5,973 ) 2007   9/15/06

11800 Tech Road (O)

   Silver Spring, MD     15,440     4,574     19,703     2,505     4,574     22,208     26,782     (6,886 ) 1989   8/1/02

1190 Winterson Road (O)

   Linthicum, MD     11,291     1,335     5,340     3,930     1,335     9,270     10,605     (4,801 ) 1987   4/30/98

1199 Winterson Road (O)

   Linthicum, MD     18,578     1,599     6,395     3,063     1,599     9,458     11,057     (4,255 ) 1988   4/30/98

1201 M Street (O)

   Washington, DC     37,479     —     49,785     1,262     —     51,047     51,047     (2,336 ) 2001   9/28/10

1201 Winterson Road (O)

   Linthicum, MD     —     1,288     5,154     460     1,288     5,614     6,902     (1,907 ) 1985   4/30/98

1220 12th Street, SE (O)

   Washington, DC     30,827     —     42,682     1,238     —     43,920     43,920     (2,168 ) 2003   9/28/10

1243 Winterson Road (L)

   Linthicum, MD     —     630     —     —     630     —     630     —   (8)   12/19/01

12515 Academy Ridge View (O)

   Colorado Springs, CO     —     2,612     7,006     —     2,612     7,006     9,618     (633 ) 2006   6/26/09

1302 Concourse Drive (O)

   Linthicum, MD     —     2,078     8,313     2,633     2,078     10,946     13,024     (4,239 ) 1996   11/18/99

1304 Concourse Drive (O)

   Linthicum, MD     9,276     1,999     12,934     362     1,999     13,296     15,295     (4,190 ) 2002   11/18/99

1306 Concourse Drive (O)

   Linthicum, MD     —     2,796     11,186     1,932     2,796     13,118     15,914     (4,540 ) 1990   11/18/99

131 National Business Parkway (O)

   Annapolis Junction, MD     7,049     1,906     7,623     2,241     1,906     9,864     11,770     (3,540 ) 1990   9/28/98

132 National Business Parkway (O)

   Annapolis Junction, MD     —     2,917     12,259     2,359     2,917     14,618     17,535     (5,970 ) 2000   5/28/99

13200 Woodland Park Road (O)

   Herndon, VA     —     10,428     41,711     13,757     10,428     55,468     65,896     (17,100 ) 2002   6/2/03

133 National Business Parkway (O)

   Annapolis Junction, MD     9,432     2,517     10,068     4,202     2,517     14,270     16,787     (5,503 ) 1997   9/28/98

1331 Ashton Road (O)

   Hanover, MD     —     587     2,346     311     587     2,657     3,244     (848 ) 1989   4/28/99

1334 Ashton Road (O)

   Hanover, MD     —     736     2,446     2,319     736     4,765     5,501     (1,820 ) 1989   4/28/99

134 National Business Parkway (O)

   Annapolis Junction, MD     19,200     3,684     7,517     1,700     3,684     9,217     12,901     (3,678 ) 1999   11/13/98

1340 Ashton Road (O)

   Hanover, MD     —     905     3,619     1,040     905     4,659     5,564     (1,755 ) 1989   4/28/99

1341 Ashton Road (O)

   Hanover, MD     —     306     1,223     566     306     1,789     2,095     (662 ) 1989   4/28/99

1343 Ashton Road (O)

   Hanover, MD     —     193     774     405     193     1,179     1,372     (355 ) 1989   4/28/99

13450 Sunrise Valley Road (O)

   Herndon, VA     —     1,386     5,576     1,818     1,386     7,394     8,780     (2,539 ) 1998   7/25/03

13454 Sunrise Valley Road (O)

   Herndon, VA     —     2,899     11,986     3,162     2,899     15,148     18,047     (3,940 ) 1998   7/25/03
 
    
    
   Initial Cost    
   Gross Amounts Carried At Close of Period    
    
    
  
 
    
    
   Costs
Capitalized
Subsequent to
Acquisition 		   
    
    
  
Property (Type)(1)
  Location   Encumbrances(2)   Land   Building and
Land
Improvements 		  Land   Building and
Land
Improvements 		  Total(3)(4)   Accumulated
Depreciation(5) 		  Year
Built or
Renovated 		  Date
Acquired(6) 		 

135 National Business Parkway (O)

   Annapolis Junction, MD     10,105     2,484     9,750     1,634     2,484     11,384     13,868     (4,611 ) 1998     12/30/98  

1362 Mellon Road (O)

   Hanover, MD     —     1,706     8,404     —     1,706     8,404     10,110     (636 ) 2006     2/10/06  

140 National Business Parkway (O)

   Annapolis Junction, MD     —     3,407     24,167     631     3,407     24,798     28,205     (5,064 ) 2003     12/31/03  

141 National Business Parkway (O)

   Annapolis Junction, MD     9,902     2,398     9,590     1,755     2,398     11,345     13,743     (4,043 ) 1990     9/28/98  

14280 Park Meadow Drive (O)

   Chantilly, VA     —     3,731     15,953     798     3,731     16,751     20,482     (4,033 ) 1999     9/29/04  

1460 Dorsey Road (L)

   Hanover, MD     —     1,800     —     —     1,800     —     1,800     —   (8)     2/28/06  

14840 Conference Center Drive (O)

   Chantilly, VA     —     1,572     8,175     37     1,572     8,212     9,784     (3,223 ) 2000     7/25/03  

14850 Conference Center Drive (O)

   Chantilly, VA     —     1,615     8,358     21     1,615     8,379     9,994     (3,262 ) 2000     7/25/03  

14900 Conference Center Drive (O)

   Chantilly, VA     —     3,436     14,402     3,192     3,436     17,594     21,030     (5,049 ) 1999     7/25/03  

15 West Gude Drive (O)

   Rockville, MD     —     3,120     16,150     3,642     3,120     19,792     22,912     (3,519 ) 1986     4/7/05  

15000 Conference Center Drive (O)

   Chantilly, VA     54,000     5,193     47,180     14,672     5,193     61,852     67,045     (18,873 ) 1989     11/30/01  

1501 South Clinton Street (O)

   Baltimore, MD     —     27,964     34,059     2,510     27,964     36,569     64,533     (3,492 ) 2006     10/27/09  

15010 Conference Center Drive (O)

   Chantilly, VA     96,000     3,500     41,921     167     3,500     42,088     45,588     (5,447 ) 2006     11/30/01  

15049 Conference Center Drive (O)

   Chantilly, VA     —     4,415     20,365     718     4,415     21,083     25,498     (6,510 ) 1997     8/14/02  

15059 Conference Center Drive (O)

   Chantilly, VA     —     5,753     13,615     1,030     5,753     14,645     20,398     (4,456 ) 2000     8/14/02  

1550 West Nursery Road (O)

   Linthicum, MD     —     14,071     16,930     —     14,071     16,930     31,001     (1,274 ) 2009     10/28/09  

1550 Westbranch Drive (O)

   McLean, VA     —     5,595     26,212     116     5,595     26,328     31,923     (1,479 ) 2002     6/28/10  

1560A Cable Ranch Road (O)

   San Antonio, TX     —     1,097     3,770     6     1,097     3,776     4,873     (537 ) 1985/2007     6/19/08  

1560B Cable Ranch Road (O)

   San Antonio, TX     —     2,299     6,545     11     2,299     6,556     8,855     (910 ) 1985/2006     6/19/08  

16442 Commerce Drive (O)

   Dahlgren, VA     2,352     613     2,582     538     613     3,120     3,733     (571 ) 2002     12/21/04  

16480 Commerce Drive (O)

   Dahlgren, VA     —     1,856     7,425     164     1,856     7,589     9,445     (1,446 ) 2000     12/28/04  

16501 Commerce Drive (O)

   Dahlgren, VA     1,923     522     2,090     176     522     2,266     2,788     (527 ) 2002     12/21/04  

16539 Commerce Drive (O)

   Dahlgren, VA     —     688     2,860     1,371     688     4,231     4,919     (996 ) 1990     12/21/04  

16541 Commerce Drive (O)

   Dahlgren, VA     —     773     3,094     1,030     773     4,124     4,897     (946 ) 1996     12/21/04  

16543 Commerce Drive (O)

   Dahlgren, VA     1,603     436     1,742     1     436     1,743     2,179     (305 ) 2002     12/21/04  

1670 North Newport Road (O)

   Colorado Springs, CO     4,480     853     6,014     581     853     6,595     7,448     (515 ) 1986/1987     9/30/05  

1751 Pinnacle Drive (O)

   McLean, VA     31,060     10,486     42,339     11,501     10,486     53,840     64,326     (14,013 ) 1989/1995     9/23/04  

1753 Pinnacle Drive (O)

   McLean, VA     25,064     8,275     34,353     8,421     8,275     42,774     51,049     (9,203 ) 1976/2004     9/23/04  

1915 Aerotech Drive (O)

   Colorado Springs, CO     3,394     556     3,094     471     556     3,565     4,121     (954 ) 1985     6/8/06  

1925 Aerotech Drive (O)

   Colorado Springs, CO     3,717     556     3,067     385     556     3,452     4,008     (623 ) 1985     6/8/06  

200 International Circle (O)

   Hunt Valley, MD     —     2,016     10,851     3,604     2,016     14,455     16,471     (3,424 ) 1987     12/22/05  

201 International Circle (O)

   Hunt Valley, MD     —     1,303     6,071     2,092     1,303     8,163     9,466     (2,028 ) 1982     12/22/05  
 
    
    
   Initial Cost    
   Gross Amounts Carried At Close of Period    
    
    
  
 
    
    
   Costs
Capitalized
Subsequent to
Acquisition 		   
    
    
  
Property (Type)(1)
  Location   Encumbrances(2)   Land   Building and
Land
Improvements 		  Land   Building and
Land
Improvements 		  Total(3)(4)   Accumulated
Depreciation(5) 		  Year
Built or
Renovated 		  Date
Acquired(6) 		 

201 Technology Drive (O)

   Lebanon, VA     —     726     31,091     60     726     31,151     31,877     (3,243 ) 2007     10/5/07  

206 Research Boulevard (O)

   Aberdeen, MD     —     1,813     15,956     —     1,813     15,956     17,769     —   (7)     9/14/07  

209 Research Boulevard (O)

   Aberdeen, MD     —     1,045     16,063     —     1,045     16,063     17,108     (458 ) 2010     9/14/07  

210 Research Boulevard (O)

   Aberdeen, MD     —     1,065     13,081     —     1,065     13,081     14,146     (192 ) 2010     9/14/07  

222 Schilling Circle (O)

   Hunt Valley, MD     —     754     857     443     754     1,300     2,054     (109 ) 1978/1997     1/10/07  

22289 Exploration Drive (O)

   Lexington Park, MD     —     1,422     5,719     820     1,422     6,539     7,961     (1,669 ) 2000     3/24/04  

22299 Exploration Drive (O)

   Lexington Park, MD     —     1,362     5,791     620     1,362     6,411     7,773     (1,866 ) 1998     3/24/04  

22300 Exploration Drive (O)

   Lexington Park, MD     —     1,094     5,038     169     1,094     5,207     6,301     (1,369 ) 1997     11/9/04  

22309 Exploration Drive (O)

   Lexington Park, MD     —     2,243     10,419     204     2,243     10,623     12,866     (3,059 ) 1984/1997     3/24/04  

224 Schilling Circle (O)

   Hunt Valley, MD     —     734     468     866     734     1,334     2,068     (262 ) 1978/1997     1/10/07  

226 Schilling Circle (O)

   Hunt Valley, MD     —     1,877     9,891     392     1,877     10,283     12,160     (2,066 ) 1980     12/22/05  

23535 Cottonwood Parkway (O)

   California, MD     —     692     3,051     223     692     3,274     3,966     (650 ) 1984     3/24/04  

2500 Riva Road (O)

   Annapolis, MD     —     2,791     12,145     1     2,791     12,146     14,937     (3,040 ) 2000     3/4/03  

2691 Technology Drive (O)

   Annapolis Junction, MD     24,000     2,098     17,334     4,934     2,098     22,268     24,366     (3,783 ) 2005     5/26/00  

2701 Technology Drive (O)

   Annapolis Junction, MD     14,044     1,737     15,266     55     1,737     15,321     17,058     (4,970 ) 2001     5/26/00  

2711 Technology Drive (O)

   Annapolis Junction, MD     19,709     2,251     21,611     1,032     2,251     22,643     24,894     (7,170 ) 2002     11/13/00  

2720 Technology Drive (O)

   Annapolis Junction, MD     24,511     3,863     29,272     36     3,863     29,308     33,171     (5,369 ) 2004     1/31/02  

2721 Technology Drive (O)

   Annapolis Junction, MD     —     4,611     14,597     33     4,611     14,630     19,241     (4,451 ) 2000     10/21/99  

2730 Hercules Road (O)

   Annapolis Junction, MD     33,327     8,737     31,612     2,829     8,737     34,441     43,178     (10,797 ) 1990     9/28/98  

2900 Towerview Road (O)

   Herndon, VA     —     3,207     16,342     5,220     3,207     21,562     24,769     (2,924 ) 1982/2008     12/20/05  

300 Sentinel Drive (O)

   Annapolis Junction, MD     —     1,517     58,445     119     1,517     58,564     60,081     (2,564 ) 2009     11/14/03  

302 Sentinel Drive (O)

   Annapolis Junction, MD     23,111     2,648     29,395     330     2,648     29,725     32,373     (2,873 ) 2007     11/14/03  

304 Sentinel Drive (O)

   Annapolis Junction, MD     37,280     3,411     24,917     105     3,411     25,022     28,433     (3,716 ) 2005     11/14/03  

306 Sentinel Drive (O)

   Annapolis Junction, MD     21,353     3,260     22,592     59     3,260     22,651     25,911     (2,973 ) 2006     11/14/03  

308 Sentinel Drive (O)

   Annapolis Junction, MD     —     1,422     25,357     —     1,422     25,357     26,779     (460 ) 2010     11/14/03  

310 The Bridge Street (O)

   Huntsville, AL     —     261     26,576     —     261     26,576     26,837     (535 ) 2009     8/4/11  

3120 Fairview Park Drive (O)

   Falls Church, VA     —     6,863     35,606     2,676     6,863     38,282     45,145     (991 ) 2008     11/23/10  

314 Sentinel Way (O)

   Annapolis Junction, MD     —     1,254     1,325     —     1,254     1,325     2,579     (116 ) 2008     11/14/03  

316 Sentinel Way (O)

   Annapolis Junction, MD     —     2,748     26,670     —     2,748     26,670     29,418     (162 ) 2011     11/14/03  

318 Sentinel Way (O)

   Annapolis Junction, MD     22,649     2,185     28,426     —     2,185     28,426     30,611     (4,138 ) 2005     11/14/03  

320 Sentinel Way (O)

   Annapolis Junction, MD     —     2,067     21,623     —     2,067     21,623     23,690     (2,148 ) 2007     11/14/03  

322 Sentinel Way (O)

   Annapolis Junction, MD     22,310     2,605     22,812     —     2,605     22,812     25,417     (2,860 ) 2006     11/14/03  

324 Sentinel Way (O)

   Annapolis Junction, MD     —     1,656     22,730     —     1,656     22,730     24,386     (796 ) 2010     6/29/06  

3535 Northrop Grumman Point (O)

   Colorado Springs, CO     18,308     —     21,380     187     —     21,567     21,567     (2,735 ) 2008     6/10/08  
 
    
    
   Initial Cost    
   Gross Amounts Carried At Close of Period    
    
    
  
 
    
    
   Costs
Capitalized
Subsequent to
Acquisition 		   
    
    
  
Property (Type)(1)
  Location   Encumbrances(2)   Land   Building and
Land
Improvements 		  Land   Building and
Land
Improvements 		  Total(3)(4)   Accumulated
Depreciation(5) 		  Year
Built or
Renovated 		  Date
Acquired(6) 		 

375 West Padonia Road (O)

   Timonium, MD     —     2,483     10,415     4,016     2,483     14,431     16,914     (4,289 ) 1986     12/21/99  

400 Professional Drive (O)

   Gaithersburg, MD     14,934     3,673     9,198     1,571     3,673     10,769     14,442     (3,053 ) 2000     3/5/04  

410 National Business Parkway (O)

   Annapolis Junction, MD     —     1,831     13,902     —     1,831     13,902     15,733     —   (7)     6/29/03  

4230 Forbes Boulevard (O)

   Lanham, MD     —     511     4,346     —     511     4,346     4,857     (1,726 ) 2003     12/24/02  

430 National Business Parkway (O)

   Annapolis Junction, MD     —     1,852     17,921     —     1,852     17,921     19,773     (38 ) 2011     6/29/06  

44408 Pecan Court (O)

   California, MD     —     817     1,993     118     817     2,111     2,928     (71 ) 1986     3/24/04  

44414 Pecan Court (O)

   California, MD     —     405     1,619     291     405     1,910     2,315     (393 ) 1986     3/24/04  

44417 Pecan Court (O)

   California, MD     —     434     1,939     72     434     2,011     2,445     (562 ) 1989     3/24/04  

44420 Pecan Court (O)

   California, MD     —     344     890     126     344     1,016     1,360     (36 ) 1989     11/9/04  

44425 Pecan Court (O)

   California, MD     —     1,309     3,506     952     1,309     4,458     5,767     (513 ) 1997     5/5/04  

45 West Gude Drive (O)

   Rockville, MD     —     3,102     11,869     10,722     3,102     22,591     25,693     (3,493 ) 1987     4/7/05  

45310 Abell House Lane (O)

   California, MD     —     2,272     14,253     —     2,272     14,253     16,525     (28 ) 2011     8/30/10  

46579 Expedition Drive (O)

   Lexington Park, MD     —     1,406     5,796     1,066     1,406     6,862     8,268     (1,848 ) 2002     3/24/04  

46591 Expedition Drive (O)

   Lexington Park, MD     —     1,200     7,199     138     1,200     7,337     8,537     (898 ) 2005     3/24/04  

4851 Stonecroft Boulevard (O)

   Chantilly, VA     —     1,878     11,558     21     1,878     11,579     13,457     (2,089 ) 2004     8/14/02  

4940 Campbell Drive (O)

   White Marsh, MD     —     1,379     3,858     830     1,379     4,688     6,067     (771 ) 1990     1/9/07  

4969 Mercantile Road (O)

   White Marsh, MD     —     1,308     4,456     62     1,308     4,518     5,826     (563 ) 1983     1/9/07  

4979 Mercantile Road (O)

   White Marsh, MD     —     1,299     4,686     81     1,299     4,767     6,066     (606 ) 1985     1/9/07  

5020 Campbell Boulevard (O)

   White Marsh, MD     —     1,014     3,136     110     1,014     3,246     4,260     (556 ) 1986 - 1988     1/9/07  

5022 Campbell Boulevard (O)

   White Marsh, MD     —     624     1,924     282     624     2,206     2,830     (400 ) 1986 - 1988     1/9/07  

5024 Campbell Boulevard (O)

   White Marsh, MD     —     767     2,420     255     767     2,675     3,442     (605 ) 1986 - 1988     1/9/07  

5026 Campbell Boulevard (O)

   White Marsh, MD     —     700     2,138     7     700     2,145     2,845     (344 ) 1986 - 1988     1/9/07  

525 Babcock Road (O)

   Colorado Springs, CO     —     355     974     32     355     1,006     1,361     (170 ) 1967     7/12/07  

5325 Nottingham Drive (O)

   White Marsh, MD     —     816     3,976     484     816     4,460     5,276     (598 ) 2002     1/9/07  

5355 Nottingham Drive (O)

   White Marsh, MD     —     761     3,562     1,599     761     5,161     5,922     (663 ) 2005     1/9/07  

5520 Research Park Drive (O)

   Catonsville, MD     —     —     20,027     —     —     20,027     20,027     (1,183 ) 2009     4/4/06  

5522 Research Park Drive (O)

   Catonsville, MD     —     —     4,550     —     —     4,550     4,550     (500 ) 2007     3/8/06  

565 Space Center Drive (O)

   Colorado Springs, CO     —     644     5,619     18     644     5,637     6,281     (562 ) 2009     7/8/05  

5725 Mark Dabling Boulevard (O)

   Colorado Springs, CO     12,882     900     11,397     2,523     900     13,920     14,820     (3,844 ) 1984     5/18/06  

5755 Mark Dabling Boulevard (O)

   Colorado Springs, CO     10,208     799     10,324     2,661     799     12,985     13,784     (2,762 ) 1989     5/18/06  

5775 Mark Dabling Boulevard (O)

   Colorado Springs, CO     12,477     1,035     12,440     1,386     1,035     13,826     14,861     (3,850 ) 1984     5/18/06  

5825 University Research Court (O)

   College Park, MD     16,605     —     21,690     —     —     21,690     21,690     (1,621 ) 2008     1/29/08  

5850 University Research Court (O)

   College Park, MD     22,609     —     30,062     —     —     30,062     30,062     (1,483 ) 2009     1/29/08  

655 Space Center Drive (O)

   Colorado Springs, CO     —     745     17,668     25     745     17,693     18,438     (1,626 ) 2008     7/8/05  

6700 Alexander Bell Drive (O)

   Columbia, MD     4,000     1,755     7,019     3,751     1,755     10,770     12,525     (4,195 ) 1988     5/14/01  

6708 Alexander Bell Drive (O)

   Columbia, MD     6,320     897     3,588     1,580     897     5,168     6,065     (2,233 ) 1988     5/14/01  
 
    
    
   Initial Cost    
   Gross Amounts Carried At Close of Period    
    
    
  
 
    
    
   Costs
Capitalized
Subsequent to
Acquisition 		   
    
    
  
Property (Type)(1)
  Location   Encumbrances(2)   Land   Building and
Land
Improvements 		  Land   Building and
Land
Improvements 		  Total(3)(4)   Accumulated
Depreciation(5) 		  Year
Built or
Renovated 		  Date
Acquired(6) 		 

6711 Columbia Gateway Drive (O)

   Columbia, MD     —     2,683     23,218     263     2,683     23,481     26,164     (2,878 ) 2006 - 2007     9/28/00  

6716 Alexander Bell Drive (O)

   Columbia, MD     —     1,242     4,969     1,948     1,242     6,917     8,159     (3,153 ) 1990     12/31/98  

6721 Columbia Gateway Drive (O)

   Columbia, MD     29,782     1,753     34,090     —     1,753     34,090     35,843     (2,381 ) 2009     9/28/00  

6724 Alexander Bell Drive (O)

   Columbia, MD     10,939     449     5,039     221     449     5,260     5,709     (1,614 ) 2001     5/14/01  

6731 Columbia Gateway Drive (O)

   Columbia, MD     —     2,807     19,098     1,017     2,807     20,115     22,922     (5,825 ) 2002     3/29/00  

6740 Alexander Bell Drive (O)

   Columbia, MD     —     1,424     5,696     2,850     1,424     8,546     9,970     (3,601 ) 1992     12/31/98  

6741 Columbia Gateway Drive (O)

   Columbia, MD     —     675     1,711     114     675     1,825     2,500     (142 ) 2008     9/28/00  

6750 Alexander Bell Drive (O)

   Columbia, MD     —     1,263     12,461     2,020     1,263     14,481     15,744     (5,400 ) 2001     12/31/98  

6760 Alexander Bell Drive (O)

   Columbia, MD     —     890     3,561     1,849     890     5,410     6,300     (2,424 ) 1991     12/31/98  

6940 Columbia Gateway Drive (O)

   Columbia, MD     17,300     3,545     9,916     2,620     3,545     12,536     16,081     (4,760 ) 1999     11/13/98  

6950 Columbia Gateway Drive (O)

   Columbia, MD     —     3,596     14,269     945     3,596     15,214     18,810     (5,612 ) 1998     10/22/98  

7000 Columbia Gateway Drive (O)

   Columbia, MD     15,800     3,131     12,103     291     3,131     12,394     15,525     (2,888 ) 1999     5/31/02  

7015 Albert Einstein Drive (O)

   Columbia, MD     2,746     2,058     6,093     826     2,058     6,919     8,977     (1,934 ) 1999     12/1/05  

7061 Columbia Gateway Drive (O)

   Columbia, MD     2,278     729     3,094     560     729     3,654     4,383     (1,314 ) 2000     8/30/01  

7063 Columbia Gateway Drive (O)

   Columbia, MD     2,732     902     3,684     1,035     902     4,719     5,621     (1,923 ) 2000     8/30/01  

7065 Columbia Gateway Drive (O)

   Columbia, MD     2,650     919     3,763     993     919     4,756     5,675     (1,715 ) 2000     8/30/01  

7067 Columbia Gateway Drive (O)

   Columbia, MD     7,728     1,829     11,823     2,033     1,829     13,856     15,685     (3,772 ) 2001     8/30/01  

7125 Columbia Gateway Drive (L)

   Columbia, MD     —     3,361     118     279     3,361     397     3,758     —   (8)     6/29/06  

7125 Columbia Gateway Drive (O)

   Columbia, MD     34,538     17,126     46,994     5,876     17,126     52,870     69,996     (8,824 ) 1973/1999     6/29/06  

7130 Columbia Gateway Drive (O)

   Columbia, MD     6,519     1,350     4,359     1,768     1,350     6,127     7,477     (1,207 ) 1989     9/19/05  

7134 Columbia Gateway Drive (O)

   Columbia, MD     2,949     704     1,971     70     704     2,041     2,745     (446 ) 1990     9/19/05  

7138 Columbia Gateway Drive (O)

   Columbia, MD     5,406     1,104     3,518     1,961     1,104     5,479     6,583     (1,852 ) 1990     9/19/05  

7142 Columbia Gateway Drive (O)

   Columbia, MD     6,280     1,342     3,978     1,664     1,342     5,642     6,984     (1,147 ) 1994     9/19/05  

7150 Columbia Gateway Drive (O)

   Columbia, MD     4,850     1,032     3,429     216     1,032     3,645     4,677     (776 ) 1991     9/19/05  

7150 Riverwood Drive (O)

   Columbia, MD     —     1,821     4,388     754     1,821     5,142     6,963     (873 ) 2000     1/10/07  

7160 Riverwood Drive (O)

   Columbia, MD     —     2,732     7,006     1,169     2,732     8,175     10,907     (2,407 ) 2000     1/10/07  

7170 Riverwood Drive (O)

   Columbia, MD     —     1,283     3,096     233     1,283     3,329     4,612     (566 ) 2000     1/10/07  

7200 Riverwood Road (O)

   Columbia, MD     —     4,089     16,356     2,348     4,089     18,704     22,793     (6,172 ) 1986     10/13/98  

7205 Riverwood Drive (O)

   Columbia, MD     —     1,367     13,015     —     1,367     13,015     14,382     —   (7)     7/27/05  

7240 Parkway Drive (O)

   Hanover, MD     —     1,496     5,985     2,921     1,496     8,906     10,402     (3,334 ) 1985     4/18/00  

 
    
    
   Initial Cost    
   Gross Amounts Carried At Close of Period    
    
    
  
 
    
    
   Costs
Capitalized
Subsequent to
Acquisition 		   
    
    
  
Property (Type)(1)
  Location   Encumbrances(2)   Land   Building and
Land
Improvements 		  Land   Building and
Land
Improvements 		  Total(3)(4)   Accumulated
Depreciation(5) 		  Year
Built or
Renovated 		  Date
Acquired(6) 		 

7272 Park Circle Drive (O)

   Hanover, MD     5,375     1,479     6,300     1,499     1,479     7,799     9,278     (1,349 ) 1991/1996     1/10/07  

7318 Parkway Drive (O)

   Hanover, MD     —     972     3,888     785     972     4,673     5,645     (1,449 ) 1984     4/16/99  

7320 Parkway Drive (O)

   Hanover, MD     7,000     905     3,570     1,140     905     4,710     5,615     (1,348 ) 1983     4/4/02  

745 Space Center Drive (O)

   Colorado Springs, CO     —     654     9,203     15     654     9,218     9,872     (1,338 ) 2006     7/8/05  

7467 Ridge Road (O)

   Hanover, MD     —     1,629     6,516     1,917     1,629     8,433     10,062     (3,045 ) 1990     4/28/99  

7468 Candlewood Drive (O)

   Hanover, MD     —     5,599     12,198     3     5,599     12,201     17,800     —   1979/1982     12/20/05  

7700 Potranco Road (O)

   San Antonio, TX     —     14,020     38,773     7     14,020     38,780     52,800     (4,733 ) 1982/1985     3/30/05  

7700-1 Potranco Road (O)

   San Antonio, TX     —     —     1,066     —     —     1,066     1,066     (81 ) 2007     3/30/05  

7700-5 Potranco Road (O)

   San Antonio, TX     —     —     1,884     —     —     1,884     1,884     (107 ) 2009     3/30/05  

7740 Milestone Parkway (O)

   Hanover, MD     16,829     3,825     26,143     —     3,825     26,143     29,968     (1,615 ) 2009     7/2/07  

7770 Backlick Road (O)

   Springfield, VA     17,875     6,387     20,614     —     6,387     20,614     27,001     —   (7)     3/10/10  

7923 Honeygo Boulevard (O)

   White Marsh, MD     —     715     1,437     350     715     1,787     2,502     (205 ) 1985     1/10/07  

7939 Honeygo Boulevard (O)

   White Marsh, MD     —     869     2,033     139     869     2,172     3,041     (236 ) 1984     1/10/07  

7941-7949 Corporate Drive (O)

   White Marsh, MD     —     2,087     3,782     12     2,087     3,794     5,881     (589 ) 1996     1/9/07  

800 International Drive (O)

   Linthicum, MD     8,408     775     3,099     1,098     775     4,197     4,972     (1,531 ) 1988     4/30/98  

8000 Potranco Road (O)

   San Antonio, TX     —     1,964     22,681     —     1,964     22,681     24,645     (614 ) 2010     1/20/06  

8003 Corporate Drive (O)

   White Marsh, MD     —     611     1,611     53     611     1,664     2,275     (270 ) 1999     1/9/07  

8007 Corporate Drive (O)

   White Marsh, MD     —     1,434     3,336     196     1,434     3,532     4,966     (637 ) 1995     1/9/07  

8010 Corporate Drive (O)

   White Marsh, MD     —     1,349     3,262     1,607     1,349     4,869     6,218     (629 ) 1998     1/9/07  

8013 Corporate Drive (O)

   White Marsh, MD     1,318     642     1,536     256     642     1,792     2,434     (323 ) 1990     1/9/07  

8015 Corporate Drive (O)

   White Marsh, MD     945     446     1,116     185     446     1,301     1,747     (255 ) 1990     1/9/07  

8019 Corporate Drive (O)

   White Marsh, MD     1,561     680     1,898     1,242     680     3,140     3,820     (469 ) 1990     1/9/07  

8020 Corporate Drive (O)

   White Marsh, MD     —     2,184     3,767     2,172     2,184     5,939     8,123     (683 ) 1997     1/9/07  

8023 Corporate Drive (O)

   White Marsh, MD     1,364     651     1,603     5     651     1,608     2,259     (223 ) 1990     1/9/07  

8029 Corporate Drive (O)

   White Marsh, MD     —     962     2,719     10     962     2,729     3,691     (524 ) 1988/2004     1/9/07  

8030 Potranco Road (O)

   San Antonio, TX     —     1,964     19,584     —     1,964     19,584     21,548     (612 ) 2010     1/20/06  

8031 Corporate Drive (O)

   White Marsh, MD     —     2,548     6,975     —     2,548     6,975     9,523     (1,225 ) 1988/2004     1/9/07  

8094 Sandpiper Circle (O)

   White Marsh, MD     —     1,960     3,716     214     1,960     3,930     5,890     (698 ) 1998     1/9/07  

8098 Sandpiper Circle (O)

   White Marsh, MD     —     1,797     3,651     71     1,797     3,722     5,519     (462 ) 1998     1/9/07  

8100 Potranco Road (L)

   San Antonio, TX     —     1,964     1,396     —     1,964     1,396     3,360     —   (8)     6/14/05  

8110 Corporate Drive (O)

   White Marsh, MD     —     2,285     10,117     29     2,285     10,146     12,431     (1,832 ) 2001     1/9/07  

8114 Sandpiper Circle (O)

   White Marsh, MD     —     1,634     608     1,201     1,634     1,809     3,443     (403 ) 1986     1/9/07  

8133 Perry Hall Boulevard (O)

   White Marsh, MD     —     850     1,950     325     850     2,275     3,125     (294 ) 1988     1/10/07  

8140 Corporate Drive (O)

   White Marsh, MD     —     2,158     8,457     1,989     2,158     10,446     12,604     (2,564 ) 2003     1/9/07  

 
    
    
   Initial Cost    
   Gross Amounts Carried At Close of Period    
    
    
  
 
    
    
   Costs
Capitalized
Subsequent to
Acquisition 		   
    
    
  
Property (Type)(1)
  Location   Encumbrances(2)   Land   Building and
Land
Improvements 		  Land   Building and
Land
Improvements 		  Total(3)(4)   Accumulated
Depreciation(5) 		  Year
Built or
Renovated 		  Date
Acquired(6) 		 

849 International Drive (O)

   Linthicum, MD     11,692     1,356     5,426     2,876     1,356     8,302     9,658     (3,742 ) 1988     2/23/99  

8615 Ridgely's Choice (O)

   White Marsh, MD     —     1,078     3,024     1,121     1,078     4,145     5,223     (447 ) 2005     1/9/07  

8621 Robert Fulton Drive (O)

   Columbia, MD     11,000     2,317     12,642     199     2,317     12,841     15,158     (1,968 ) 2005 - 2006     6/10/05  

8661 Robert Fulton Drive (O)

   Columbia, MD     6,200     1,510     3,764     1,042     1,510     4,806     6,316     (1,361 ) 2002     12/30/03  

8671 Robert Fulton Drive (O)

   Columbia, MD     7,600     1,718     4,280     1,941     1,718     6,221     7,939     (1,848 ) 2002     12/30/03  

870 Elkridge Landing Road (O)

   Linthicum, MD     18,900     2,003     9,442     6,689     2,003     16,131     18,134     (6,712 ) 1981     8/3/01  

881 Elkridge Landing Road (O)

   Linthicum, MD     11,812     1,034     4,137     1,049     1,034     5,186     6,220     (1,816 ) 1986     4/30/98  

891 Elkridge Landing Road (O)

   Linthicum, MD     —     1,160     4,750     1,777     1,160     6,527     7,687     (2,378 ) 1984     7/2/01  

900 Elkridge Landing Road (O)

   Linthicum, MD     —     1,993     7,972     2,495     1,993     10,467     12,460     (4,260 ) 1982     4/30/98  

900 International Drive (O)

   Linthicum, MD     8,008     981     3,922     834     981     4,756     5,737     (1,791 ) 1986     4/30/98  

901 Elkridge Landing Road (O)

   Linthicum, MD     —     1,151     4,416     1,563     1,151     5,979     7,130     (1,914 ) 1984     7/2/01  

9020 Mendenhall Court (O)

   Columbia, MD     —     1,233     2,694     392     1,233     3,086     4,319     (481 ) 1982/2005     1/9/07  

911 Elkridge Landing Road (O)

   Linthicum, MD     —     1,215     4,861     2,024     1,215     6,885     8,100     (2,564 ) 1985     4/30/98  

9130 Guilford Road (O)

   Columbia, MD     771     230     939     101     230     1,040     1,270     (333 ) 1984     4/4/02  

9140 Guilford Road (O)

   Columbia, MD     2,639     794     3,209     791     794     4,000     4,794     (1,320 ) 1983     4/4/02  

9150 Guilford Road (O)

   Columbia, MD     1,062     319     1,291     318     319     1,609     1,928     (555 ) 1984     4/4/02  

9160 Guilford Road (O)

   Columbia, MD     2,209     665     2,686     1,304     665     3,990     4,655     (1,853 ) 1984     4/4/02  

920 Elkridge Landing Road (O)

   Linthicum, MD     7,025     2,101     9,765     687     2,101     10,452     12,553     (3,844 ) 1982     7/2/01  

921 Elkridge Landing Road (O)

   Linthicum, MD     —     1,044     4,176     639     1,044     4,815     5,859     (1,864 ) 1983     4/30/98  

930 International Drive (O)

   Linthicum, MD     8,488     1,013     4,053     1,100     1,013     5,153     6,166     (2,024 ) 1986     4/30/98  

938 Elkridge Landing Road (O)

   Linthicum, MD     3,899     1,204     4,727     346     1,204     5,073     6,277     (1,423 ) 1984     7/2/01  

939 Elkridge Landing Road (O)

   Linthicum, MD     —     939     3,756     1,742     939     5,498     6,437     (2,241 ) 1983     4/30/98  

940 Elkridge Landing Road (L)

   Linthicum, MD     2,960     1,100     4,700     170     1,100     4,870     5,970     (4,879 ) (8)     7/2/01  

9651 Hornbaker Road (D)

   Manassas, VA     —     6,050     187,441     54     6,050     187,495     193,545     (967 ) 2010     9/14/10  

9690 Deereco Road (O)

   Timonium, MD     —     3,415     13,723     4,955     3,415     18,678     22,093     (7,246 ) 1988     12/21/99  

9700 Patuxent Woods Drive (O)

   Columbia, MD     2,001     1,329     2,668     446     1,329     3,114     4,443     (629 ) 1986/2001     1/9/07  

9710 Patuxent Woods Drive (O)

   Columbia, MD     966     648     1,425     254     648     1,679     2,327     (293 ) 1986/2001     1/9/07  

9720 Patuxent Woods Drive (O)

   Columbia, MD     2,638     1,701     1,915     1,295     1,701     3,210     4,911     (772 ) 1986/2001     1/9/07  

9730 Patuxent Woods Drive (O)

   Columbia, MD     2,038     1,318     2,782     143     1,318     2,925     4,243     (646 ) 1986/2001     1/9/07  

9740 Patuxent Woods Drive (O)

   Columbia, MD     2,447     1,628     3,052     755     1,628     3,807     5,435     (750 ) 1986/2001     1/9/07  

980 Technology Court (O)

   Colorado Springs, CO     —     526     2,046     365     526     2,411     2,937     (520 ) 1995     9/28/05  

985 Space Center Drive (O)

   Colorado Springs, CO     —     777     12,287     1,501     777     13,788     14,565     (2,557 ) 1989     9/28/05  

9900 Franklin Square Drive (O)

   White Marsh, MD     —     979     3,466     161     979     3,627     4,606     (614 ) 1999     1/9/07  

9910 Franklin Square Drive (O)

   White Marsh, MD     5,200     1,219     6,590     25     1,219     6,615     7,834     (1,213 ) 2005     1/9/07  

9920 Franklin Square Drive (O)

   White Marsh, MD     —     1,058     5,293     1,313     1,058     6,606     7,664     (1,141 ) 2006     1/9/07  

 
    
    
   Initial Cost    
   Gross Amounts Carried At Close of Period    
    
    
  
 
    
    
   Costs
Capitalized
Subsequent to
Acquisition 		   
    
    
  
Property (Type)(1)
  Location   Encumbrances(2)   Land   Building and
Land
Improvements 		  Land   Building and
Land
Improvements 		  Total(3)(4)   Accumulated
Depreciation(5) 		  Year
Built or
Renovated 		  Date
Acquired(6) 		 

9925 Federal Drive (O)

   Colorado Springs, CO     —     1,129     5,166     17     1,129     5,183     6,312     (590 ) 2008     9/28/05  

9930 Franklin Square Drive (O)

   White Marsh, MD     —     1,137     3,921     20     1,137     3,941     5,078     (702 ) 2001     1/9/07  

9940 Franklin Square Drive (O)

   White Marsh, MD     —     1,052     3,382     281     1,052     3,663     4,715     (587 ) 2000     1/9/07  

9945 Federal Drive (O)

   Colorado Springs, CO     —     1,854     1,075     —     1,854     1,075     2,929     (429 ) 2009     9/28/05  

9950 Federal Drive (O)

   Colorado Springs, CO     —     877     5,045     1,501     877     6,546     7,423     (1,705 ) 2001     12/22/05  

9960 Federal Drive (O)

   Colorado Springs, CO     —     695     2,853     290     695     3,143     3,838     (749 ) 2001     12/22/05  

9965 Federal Drive (L)

   Colorado Springs, CO     —     466     —     —     466     —     466     —   (8)     12/22/05  

9965 Federal Drive (O)

   Colorado Springs, CO     —     1,401     6,061     555     1,401     6,616     8,017     (775 ) 1983/2007     1/19/06  

999 Corporate Boulevard (O)

   Linthicum, MD     13,533     1,187     8,332     556     1,187     8,888     10,075     (2,912 ) 2000     8/1/99  

Aerotech Commerce (L)

   Colorado Springs, CO     —     900     —     —     900     —     900     —   (8)     5/19/06  

Arborcrest (O)

   Blue Bell, PA     —     22,370     142,202     1,054     22,370     143,256     165,626     (32,702 ) 1991 - 1996(6)(7)     10/14/97  

Arundel Preserve (L)

   Hanover, MD     —     —     5,296     —     —     5,296     5,296     —   (8)     (9 )

Canton Crossing Land (L)

   Baltimore, MD     —     16,085     1,038     —     16,085     1,038     17,123     —   (8)     10/27/09  

Canton Crossing Util Distr Ctr (O)

   Baltimore, MD     —     7,300     15,551     490     7,300     16,041     23,341     (1,132 ) 2005     10/27/09  

Columbia Gateway Parcel T-11 (L)

   Columbia, MD     —     6,387     2,931     —     6,387     2,931     9,318     —   (8)     9/20/04  

Dahlgren Technology Center (L)

   Dahlgren, VA     —     1,083     167     —     1,083     167     1,250     —   (8)     3/16/05  

Expedition VII (L)

   Lexington Park, MD     —     705     735     —     705     735     1,440     —   (8)     3/24/04  

Fort Ritchie (L)

   Cascade, MD     —     1,026     —     —     1,026     —     1,026     —   (8)     10/5/06  

Indian Head (L)

   Bryans Road, MD     —     6,436     73     —     6,436     73     6,509     —   (8)     10/23/06  

InterQuest (L)

   Colorado Springs, CO     —     14,515     19     —     14,515     19     14,534     —   (8)     9/28/05  

M Square Research Park (L)

   College Park, MD     —     —     3,011     —     —     3,011     3,011     —   (8)     1/29/08  

Military Drive (L)

   San Antonio, TX     —     9,460     4,304     —     9,460     4,304     13,764     —   (8)     3/30/05  

National Business Park (L)

   Annapolis Junction, MD     —     5,510     8,497     —     5,510     8,497     14,007     —   (8)     11/14/03  

National Business Park North (L)

   Jessup, MD     —     27,118     25,047     —     27,118     25,047     52,165     —   (8)     6/29/06  

North Gate Business Park (L)

   Aberdeen, MD     —     6,486     9,783     —     6,486     9,783     16,269     —   (8)     9/14/07  

Northwest Crossroads (L)

   San Antonio, TX     —     7,430     836     —     7,430     836     8,266     —   (8)     1/20/06  

Old Annapolis Road (O)

   Columbia, MD     —     1,637     5,500     2,103     1,637     7,603     9,240     (2,113 ) 1974/1985     12/14/00  

Patriot Park (L)

   Colorado Springs, CO     —     8,768     232     —     8,768     232     9,000     —   (8)     7/8/05  

Patriot Ridge (L)

   Springfield, VA     —     18,517     25,576     —     18,517     25,576     44,093     —   (8)     3/10/10  

Redstone Gateway (L)

   Huntsville, AL     —     —     15,879     —     —     15,879     15,879     —   (8)     3/23/10  

Riverwood (L)

   Columbia, MD     —     1,788     959     —     1,788     959     2,747     (122 ) (8)     7/27/05  

 
    
    
   Initial Cost    
   Gross Amounts Carried At Close of Period    
    
    
  
 
    
    
   Costs
Capitalized
Subsequent to
Acquisition 		   
    
    
  
Property (Type)(1)
  Location   Encumbrances(2)   Land   Building and
Land
Improvements 		  Land   Building and
Land
Improvements 		  Total(3)(4)   Accumulated
Depreciation(5) 		  Year
Built or
Renovated 		  Date
Acquired(6) 		 

Rockville Corporate Center (L)

   Rockville, MD     —     2,872     —     —     2,872     —     2,872     —   (8)     4/7/05  

Route 15/Biggs Ford Road (L)

   Frederick, MD     —     8,703     509     —     8,703     509     9,212     —   (8)     8/28/08  

Thomas Johnson Drive (L)

   Frederick, MD     —     1,092     1,219     —     1,092     1,219     2,311     —   (8)     10/21/05  

West Nursery Road (L)

   Linthicum, MD     —     1,441     —     —     1,441     —     1,441     —   (8)     10/28/09  

Westfields—Park Center (L)

   Herndon, VA     —     3,609     2,654     —     3,609     2,654     6,263     —   (8)     7/18/02  

Westfields Corporate Center (L)

   Herndon, VA     —     7,141     1,333     —     7,141     1,333     8,474     —   (8)     7/31/02  

White Marsh (L)

   White Marsh, MD     —     30,322     11,497     —     30,322     11,497     41,819     —   (8)     1/9/07  

Woodland Park (L)

   Herndon, VA     —     9,614     81     —     9,614     81     9,695     —   (8)     4/29/04  

Other Developments, including intercompany eliminations (V)

   Various     —     7     (152 )   (438 )   7     (590 )   (583 )   699   Various     Various  
                                                 

 

       $ 1,129,611   $ 727,222   $ 3,022,002   $ 289,708   $ 727,222   $ 3,311,710   $ 4,038,932   $ (577,601 )          
                                                 
(1)
A legend for the Property Type follows: (O) = Office Property; (L) = Land held or under pre-construction; (D) = Data Center; and (V) = Various.

(2)
Excludes our unsecured Revolving Credit Facility of $662.0 million, senior exchangeable notes of $227.3 million, unsecured notes payable of $5.1 million, and net premiums on the remaining loans of $2.4 million.

(3)
The aggregate cost of these assets for Federal income tax purposes was approximately $3.6 billion at December 31, 2011.

(4)
As discussed in Note 5 to our Consolidated Financial Statements, we recognized impairment losses of $122.5 million in connection with certain properties included in our Strategic Reallocation Plan and $27.7 million in connection with our property in Cascade, Maryland known as Fort Ritchie.

(5)
The estimated lives over which depreciation is recognized follow: Building and land improvements: 10-40 years; and tenant improvements: related lease terms.

(6)
The acquisition date of multi-parcel properties reflects the date of the earliest parcel acquisition.

(7)
Under construction or redevelopment at December 31, 2011.

(8)
Held or under pre-construction at December 31, 2011.

(9)
Development in progress in anticipation of acquisition.

        The following table summarizes our changes in cost of properties for the years ended December 31, 2011, 2010 and 2009 (in thousands):

 
   2011   2010   2009  

Beginning balance

   $ 3,948,487   $ 3,452,512   $ 3,121,576  

Acquisitions of operating properties

     26,887     187,052     119,249  

Improvements and other additions

     304,079     338,358     211,752  

Sales

     (75,315 )   (29,430 )   (65 )

Impairments

     (165,206 )   —     —  

Other

     —     (5 )   —  
               

Ending balance

   $ 4,038,932   $ 3,948,487   $ 3,452,512  
               

        The following table summarizes our changes in accumulated depreciation for the same time periods (in thousands):

 
   2011   2010   2009  

Beginning balance

   $ 503,032   $ 422,612   $ 343,110  

Depreciation expense

     99,173     88,048     79,650  

Sales

     (9,640 )   (7,764 )   —  

Impairments

     (15,039 )   —     —  

Other

     75     136     (148 )
               

Ending balance

   $ 577,601   $ 503,032   $ 422,612