Schedule III-Real Estate and Accumulated Depreciation

v2.4.0.6

Schedule III-Real Estate and Accumulated Depreciation	12 Months Ended
	Dec. 31, 2012
Real Estate and Accumulated Depreciation Disclosure [Abstract]
Schedule III-Real Estate and Accumulated Depreciation	Corporate Office Properties Trust Schedule III—Real Estate and Accumulated Depreciation December 31, 2012 (Dollars in thousands)       Initial Cost   Gross Amounts Carried At Close of Period       Property (Type) (1) Location Encumbrances (2) Land Building and Land Improvements Costs Capitalized Subsequent to Acquisition Land Building and Land Improvements Total (3)(4) Accumulated Depreciation (5) Year Built or Renovated Date Acquired (6) 1000 Redstone Gateway (O) Huntsville, AL $ 11,078 $ — $ 18,582 $ — $ — $ 18,582 $ 18,582 $ — (7) 3/23/2010 1055 North Newport Road (O)(10) Colorado Springs, CO — 972 5,708 — 972 5,708 6,680 (178 ) 2007-2008 5/19/2006 10807 New Allegiance Drive (O)(10) Colorado Springs, CO — 1,840 15,439 122 1,840 15,561 17,401 (298 ) 2009 9/28/2005 1099 Winterson Road (O) Linthicum, MD 12,012 1,323 5,293 2,499 1,323 7,792 9,115 (3,348 ) 1988 4/30/1998 1100 Redstone Gateway (O) Huntsville, AL — — 924 — — 924 924 — (7) 3/23/2010 114 National Business Parkway (O) Annapolis Junction, MD — 364 3,109 21 364 3,130 3,494 (878 ) 2002 6/30/2000 11751 Meadowville Lane (O) Richmond, VA — 1,305 52,098 112 1,305 52,210 53,515 (7,278 ) 2007 9/15/2006 1190 Winterson Road (O) Linthicum, MD 11,291 1,335 5,340 4,025 1,335 9,365 10,700 (5,111 ) 1987 4/30/1998 1199 Winterson Road (O) Linthicum, MD 18,578 1,599 6,395 3,266 1,599 9,661 11,260 (4,665 ) 1988 4/30/1998 1200 Redstone Gateway (O) Huntsville, AL — — 2,297 — — 2,297 2,297 — (7) 3/23/2010 1201 M Street (O) Washington, DC 36,659 — 49,785 1,959 — 51,744 51,744 (3,939 ) 2001 9/28/2010 1201 Winterson Road (O) Linthicum, MD — 1,288 5,154 460 1,288 5,614 6,902 (2,068 ) 1985 4/30/1998 1220 12th Street, SE (O) Washington, DC 30,153 — 42,464 733 — 43,197 43,197 (3,914 ) 2003 9/28/2010 1243 Winterson Road (L) Linthicum, MD — 630 — — 630 — 630 — (8) 12/19/2001 12515 Academy Ridge View (O)(10) Colorado Springs, CO — 2,612 6,087 — 2,612 6,087 8,699 (441 ) 2006 6/26/2009 1302 Concourse Drive (O) Linthicum, MD — 2,078 8,313 2,991 2,078 11,304 13,382 (4,626 ) 1996 11/18/1999 1304 Concourse Drive (O) Linthicum, MD — 1,999 12,934 1,202 1,999 14,136 16,135 (4,657 ) 2002 11/18/1999 1306 Concourse Drive (O) Linthicum, MD — 2,796 11,186 2,837 2,796 14,023 16,819 (4,998 ) 1990 11/18/1999 131 National Business Parkway (O) Annapolis Junction, MD 6,922 1,906 7,623 2,657 1,906 10,280 12,186 (3,876 ) 1990 9/28/1998 132 National Business Parkway (O) Annapolis Junction, MD — 2,917 12,259 2,895 2,917 15,154 18,071 (6,563 ) 2000 5/28/1999 13200 Woodland Park Road (O) Herndon, VA — 10,428 41,711 13,831 10,428 55,542 65,970 (19,432 ) 2002 6/2/2003 133 National Business Parkway (O) Annapolis Junction, MD 9,262 2,517 10,068 4,821 2,517 14,889 17,406 (6,167 ) 1997 9/28/1998 1331 Ashton Road (O) Hanover, MD — 587 2,347 677 587 3,024 3,611 (939 ) 1989 4/28/1999 1334 Ashton Road (O) Hanover, MD — 736 1,488 2,301 736 3,789 4,525 (1,468 ) 1989 4/28/1999 134 National Business Parkway (O) Annapolis Junction, MD 19,200 3,684 7,517 2,230 3,684 9,747 13,431 (4,138 ) 1999 11/13/1998 1340 Ashton Road (O) Hanover, MD — 905 3,620 1,067 905 4,687 5,592 (1,874 ) 1989 4/28/1999 1341 Ashton Road (O) Hanover, MD — 306 1,223 588 306 1,811 2,117 (727 ) 1989 4/28/1999 1343 Ashton Road (O) Hanover, MD — 193 774 405 193 1,179 1,372 (435 ) 1989 4/28/1999 13450 Sunrise Valley Road (O) Herndon, VA — 1,386 5,576 2,722 1,386 8,298 9,684 (2,853 ) 1998 7/25/2003 13454 Sunrise Valley Road (O) Herndon, VA — 2,899 11,986 3,909 2,899 15,895 18,794 (4,605 ) 1998 7/25/2003 135 National Business Parkway (O) Annapolis Junction, MD 9,925 2,484 9,750 2,882 2,484 12,632 15,116 (4,932 ) 1998 12/30/1998 1362 Mellon Road (O) Hanover, MD — 1,706 8,412 18 1,706 8,430 10,136 (841 ) 2006 2/10/2006 13857 McLearen Road (O) Herndon, VA — 3,507 30,177 1,724 3,507 31,901 35,408 (973 ) 2007 7/11/2012 140 National Business Parkway (O) Annapolis Junction, MD — 3,407 24,167 643 3,407 24,810 28,217 (5,748 ) 2003 12/31/2003       Initial Cost   Gross Amounts Carried At Close of Period       Property (Type) (1) Location Encumbrances (2) Land Building and Land Improvements Costs Capitalized Subsequent to Acquisition Land Building and Land Improvements Total (3)(4) Accumulated Depreciation (5) Year Built or Renovated Date Acquired (6) 141 National Business Parkway (O) Annapolis Junction, MD 9,725 2,398 9,590 2,389 2,398 11,979 14,377 (4,354 ) 1990 9/28/1998 14280 Park Meadow Drive (O) Chantilly, VA — 3,731 15,953 1,009 3,731 16,962 20,693 (4,529 ) 1999 9/29/2004 1460 Dorsey Road (L) Hanover, MD — 1,800 — — 1,800 — 1,800 — (8) 2/28/2006 14840 Conference Center Drive (O) Chantilly, VA — 1,572 8,175 508 1,572 8,683 10,255 (3,385 ) 2000 7/25/2003 14850 Conference Center Drive (O) Chantilly, VA — 1,615 8,358 539 1,615 8,897 10,512 (3,434 ) 2000 7/25/2003 14900 Conference Center Drive (O) Chantilly, VA — 3,436 14,402 3,560 3,436 17,962 21,398 (5,796 ) 1999 7/25/2003 15000 Conference Center Drive (O) Chantilly, VA 54,000 5,193 47,045 18,198 5,193 65,243 70,436 (20,752 ) 1989 11/30/2001 1501 South Clinton Street (O) Baltimore, MD — 27,964 50,415 5,222 27,964 55,637 83,601 (5,696 ) 2006 10/27/2009 15010 Conference Center Drive (O) Chantilly, VA 96,000 3,500 41,921 344 3,500 42,265 45,765 (6,503 ) 2006 11/30/2001 15049 Conference Center Drive (O) Chantilly, VA — 4,415 20,365 726 4,415 21,091 25,506 (7,276 ) 1997 8/14/2002 15059 Conference Center Drive (O) Chantilly, VA — 5,753 13,615 1,423 5,753 15,038 20,791 (4,891 ) 2000 8/14/2002 1550 West Nursery Road (O) Linthicum, MD — 14,071 16,930 — 14,071 16,930 31,001 (1,862 ) 2009 10/28/2009 1550 Westbranch Drive (O) McLean, VA — 5,595 26,212 116 5,595 26,328 31,923 (2,354 ) 2002 6/28/2010 1560A Cable Ranch Road (O) San Antonio, TX — 1,097 3,770 28 1,097 3,798 4,895 (667 ) 1985/2007 6/19/2008 1560B Cable Ranch Road (O) San Antonio, TX — 2,299 6,545 11 2,299 6,556 8,855 (1,120 ) 1985/2006 6/19/2008 16442 Commerce Drive (O) Dahlgren, VA 2,305 613 2,582 555 613 3,137 3,750 (761 ) 2002 12/21/2004 16480 Commerce Drive (O) Dahlgren, VA — 1,856 7,425 164 1,856 7,589 9,445 (1,649 ) 2000 12/28/2004 16501 Commerce Drive (O) Dahlgren, VA 1,885 522 2,090 185 522 2,275 2,797 (594 ) 2002 12/21/2004 16539 Commerce Drive (O) Dahlgren, VA — 688 2,860 1,443 688 4,303 4,991 (1,224 ) 1990 12/21/2004 16541 Commerce Drive (O) Dahlgren, VA — 773 3,094 1,321 773 4,415 5,188 (1,149 ) 1996 12/21/2004 16543 Commerce Drive (O) Dahlgren, VA 1,571 436 1,742 12 436 1,754 2,190 (349 ) 2002 12/21/2004 1670 North Newport Road (O)(10) Colorado Springs, CO 4,383 853 5,188 763 853 5,951 6,804 (776 ) 1986/1987 9/30/2005 1751 Pinnacle Drive (O) McLean, VA 30,283 10,486 42,339 12,461 10,486 54,800 65,286 (16,190 ) 1989/1995 9/23/2004 1753 Pinnacle Drive (O) McLean, VA 24,438 8,275 34,353 8,736 8,275 43,089 51,364 (10,657 ) 1976/2004 9/23/2004 1915 Aerotech Drive (O) Colorado Springs, CO 3,394 556 3,094 539 556 3,633 4,189 (1,037 ) 1985 6/8/2006 1925 Aerotech Drive (O) Colorado Springs, CO 3,717 556 3,067 343 556 3,410 3,966 (759 ) 1985 6/8/2006 201 Technology Drive (O) Lebanon, VA — 726 31,091 60 726 31,151 31,877 (4,021 ) 2007 10/5/2007 206 Research Boulevard (O) Aberdeen, MD — 1,813 17,334 — 1,813 17,334 19,147 (107 ) 2012 9/14/2007 209 Research Boulevard (O) Aberdeen, MD — 1,045 16,063 — 1,045 16,063 17,108 (859 ) 2010 9/14/2007 210 Research Boulevard (O) Aberdeen, MD — 1,065 13,144 — 1,065 13,144 14,209 (519 ) 2010 9/14/2007 22289 Exploration Drive (O) Lexington Park, MD — 1,422 5,719 1,005 1,422 6,724 8,146 (1,951 ) 2000 3/24/2004 22299 Exploration Drive (O) Lexington Park, MD — 1,362 5,791 682 1,362 6,473 7,835 (2,026 ) 1998 3/24/2004 22300 Exploration Drive (O) Lexington Park, MD — 1,094 5,038 169 1,094 5,207 6,301 (1,569 ) 1997 11/9/2004 22309 Exploration Drive (O) Lexington Park, MD — 2,243 10,419 227 2,243 10,646 12,889 (3,459 ) 1984/1997 3/24/2004 23535 Cottonwood Parkway (O) California, MD — 692 3,051 223 692 3,274 3,966 (789 ) 1984 3/24/2004 2500 Riva Road (O) Annapolis, MD — 2,791 12,145 1 2,791 12,146 14,937 (3,384 ) 2000 3/4/2003 2691 Technology Drive (O) Annapolis Junction, MD 24,000 2,098 17,334 5,096 2,098 22,430 24,528 (5,167 ) 2005 5/26/2000 2701 Technology Drive (O) Annapolis Junction, MD 13,794 1,737 15,266 306 1,737 15,572 17,309 (5,403 ) 2001 5/26/2000 2711 Technology Drive (O) Annapolis Junction, MD 19,359 2,251 21,611 1,075 2,251 22,686 24,937 (7,961 ) 2002 11/13/2000       Initial Cost   Gross Amounts Carried At Close of Period       Property (Type) (1) Location Encumbrances (2) Land Building and Land Improvements Costs Capitalized Subsequent to Acquisition Land Building and Land Improvements Total (3)(4) Accumulated Depreciation (5) Year Built or Renovated Date Acquired (6) 2720 Technology Drive (O) Annapolis Junction, MD 24,068 3,863 29,272 88 3,863 29,360 33,223 (6,102 ) 2004 1/31/2002 2721 Technology Drive (O) Annapolis Junction, MD — 4,611 14,597 1,497 4,611 16,094 20,705 (4,841 ) 2000 10/21/1999 2730 Hercules Road (O) Annapolis Junction, MD 32,734 8,737 31,612 5,277 8,737 36,889 45,626 (11,825 ) 1990 9/28/1998 2900 Towerview Road (O) Herndon, VA — 3,207 16,344 5,607 3,207 21,951 25,158 (3,785 ) 1982/2008 12/20/2005 300 Sentinel Drive (O) Annapolis Junction, MD — 1,517 58,642 119 1,517 58,761 60,278 (4,026 ) 2009 11/14/2003 302 Sentinel Drive (O) Annapolis Junction, MD 22,693 2,648 29,398 380 2,648 29,778 32,426 (3,642 ) 2007 11/14/2003 304 Sentinel Drive (O) Annapolis Junction, MD 37,280 3,411 24,917 132 3,411 25,049 28,460 (4,361 ) 2005 11/14/2003 306 Sentinel Drive (O) Annapolis Junction, MD 20,973 3,260 22,592 110 3,260 22,702 25,962 (3,541 ) 2006 11/14/2003 308 Sentinel Drive (O) Annapolis Junction, MD — 1,422 26,197 — 1,422 26,197 27,619 (1,085 ) 2010 11/14/2003 310 The Bridge Street (O) Huntsville, AL — 261 26,576 26 261 26,602 26,863 (2,028 ) 2009 8/4/2011 312 Sentinel Way (O) Annapolis Junction, MD — 3,138 9,128 — 3,138 9,128 12,266 — (7) 11/14/2003 3120 Fairview Park Drive (O) Falls Church, VA — 6,863 35,606 5,406 6,863 41,012 47,875 (2,247 ) 2008 11/23/2010 314 Sentinel Way (O) Annapolis Junction, MD — 1,254 1,325 — 1,254 1,325 2,579 (149 ) 2008 11/14/2003 316 Sentinel Way (O) Annapolis Junction, MD — 2,748 31,861 131 2,748 31,992 34,740 (830 ) 2011 11/14/2003 318 Sentinel Way (O) Annapolis Junction, MD 22,240 2,185 28,426 — 2,185 28,426 30,611 (4,849 ) 2005 11/14/2003 320 Sentinel Way (O) Annapolis Junction, MD — 2,067 21,623 — 2,067 21,623 23,690 (2,688 ) 2007 11/14/2003 322 Sentinel Way (O) Annapolis Junction, MD 21,912 2,605 22,827 — 2,605 22,827 25,432 (3,431 ) 2006 11/14/2003 324 Sentinel Way (O) Annapolis Junction, MD — 1,656 23,005 — 1,656 23,005 24,661 (1,352 ) 2010 6/29/2006 3535 Northrop Grumman Pt. (O)(10) Colorado Springs, CO 17,982 — 18,388 121 — 18,509 18,509 (1,555 ) 2008 6/10/2008 375 West Padonia Road (O) Timonium, MD — 2,483 10,415 4,821 2,483 15,236 17,719 (5,242 ) 1986 12/21/1999 410 National Business Parkway (O) Annapolis Junction, MD — 1,831 16,569 — 1,831 16,569 18,400 (34 ) 2012 6/29/2003 420 National Business Parkway (O) Annapolis Junction, MD — 2,370 15,673 — 2,370 15,673 18,043 — (7) 6/29/2006 4230 Forbes Boulevard (O)(10) Lanham, MD — 511 4,346 192 511 4,538 5,049 (1,837 ) 2003 12/24/2002 430 National Business Parkway (O) Annapolis Junction, MD — 1,852 21,038 — 1,852 21,038 22,890 (449 ) 2011 6/29/2006 44408 Pecan Court (O) California, MD — 817 1,583 118 817 1,701 2,518 (161 ) 1986 3/24/2004 44414 Pecan Court (O) California, MD — 405 1,619 336 405 1,955 2,360 (475 ) 1986 3/24/2004 44417 Pecan Court (O) California, MD — 434 1,939 88 434 2,027 2,461 (636 ) 1989 3/24/2004 44420 Pecan Court (O) California, MD — 344 890 126 344 1,016 1,360 (90 ) 1989 11/9/2004 44425 Pecan Court (O) California, MD — 1,309 3,506 1,217 1,309 4,723 6,032 (921 ) 1997 5/5/2004 45310 Abell House Lane (O) California, MD — 2,272 13,794 — 2,272 13,794 16,066 (368 ) 2011 8/30/2010 46579 Expedition Drive (O) Lexington Park, MD — 1,406 5,796 1,078 1,406 6,874 8,280 (2,147 ) 2002 3/24/2004 46591 Expedition Drive (O) Lexington Park, MD — 1,200 7,199 656 1,200 7,855 9,055 (1,083 ) 2005 3/24/2004 4851 Stonecroft Boulevard (O) Chantilly, VA — 1,878 11,558 21 1,878 11,579 13,457 (2,379 ) 2004 8/14/2002 4940 Campbell Drive (O) White Marsh, MD — 1,379 3,858 987 1,379 4,845 6,224 (933 ) 1990 1/9/2007 4969 Mercantile Road (O) White Marsh, MD — 1,308 4,456 62 1,308 4,518 5,826 (678 ) 1983 1/9/2007 4979 Mercantile Road (O) White Marsh, MD — 1,299 4,686 84 1,299 4,770 6,069 (727 ) 1985 1/9/2007 5020 Campbell Boulevard (O) White Marsh, MD — 1,014 3,136 781 1,014 3,917 4,931 (673 ) 1986-1988 1/9/2007 5022 Campbell Boulevard (O) White Marsh, MD — 624 1,924 332 624 2,256 2,880 (496 ) 1986-1988 1/9/2007 5024 Campbell Boulevard (O) White Marsh, MD — 767 2,420 250 767 2,670 3,437 (702 ) 1986-1988 1/9/2007       Initial Cost   Gross Amounts Carried At Close of Period       Property (Type) (1) Location Encumbrances (2) Land Building and Land Improvements Costs Capitalized Subsequent to Acquisition Land Building and Land Improvements Total (3)(4) Accumulated Depreciation (5) Year Built or Renovated Date Acquired (6) 5026 Campbell Boulevard (O) White Marsh, MD — 700 2,138 45 700 2,183 2,883 (396 ) 1986-1988 1/9/2007 525 Babcock Road (O)(10) Colorado Springs, CO — 355 397 79 355 476 831 (89 ) 1967 7/12/2007 5325 Nottingham Drive (O) White Marsh, MD — 816 3,976 485 816 4,461 5,277 (763 ) 2002 1/9/2007 5355 Nottingham Drive (O) White Marsh, MD — 761 3,562 1,616 761 5,178 5,939 (1,380 ) 2005 1/9/2007 5520 Research Park Drive (O) Catonsville, MD — — 20,066 — — 20,066 20,066 (1,679 ) 2009 4/4/2006 5522 Research Park Drive (O) Catonsville, MD — — 4,550 — — 4,550 4,550 (614 ) 2007 3/8/2006 565 Space Center Drive (O)(10) Colorado Springs, CO — 644 6,284 352 644 6,636 7,280 (107 ) 2009 7/8/2005 5725 Mark Dabling Boulevard (O) Colorado Springs, CO 12,882 900 11,397 2,832 900 14,229 15,129 (4,567 ) 1984 5/18/2006 5755 Mark Dabling Boulevard (O) Colorado Springs, CO 10,208 799 10,324 3,597 799 13,921 14,720 (3,464 ) 1989 5/18/2006 5775 Mark Dabling Boulevard (O) Colorado Springs, CO 12,477 1,035 12,440 1,658 1,035 14,098 15,133 (4,260 ) 1984 5/18/2006 5825 University Research Court (O) College Park, MD 16,292 — 22,190 11 — 22,201 22,201 (2,118 ) 2008 1/29/2008 5850 University Research Court (O) College Park, MD 22,183 — 30,273 57 — 30,330 30,330 (2,236 ) 2008 1/29/2008 655 Space Center Drive (O)(10) Colorado Springs, CO — 745 15,445 59 745 15,504 16,249 — 2008 7/8/2005 6700 Alexander Bell Drive (O) Columbia, MD 4,000 1,755 7,019 4,628 1,755 11,647 13,402 (4,568 ) 1988 5/14/2001 6708 Alexander Bell Drive (O) Columbia, MD 6,320 897 3,588 1,592 897 5,180 6,077 (2,440 ) 1988 5/14/2001 6711 Columbia Gateway Drive (O) Columbia, MD — 2,683 23,239 314 2,683 23,553 26,236 (3,503 ) 2006-2007 9/28/2000 6716 Alexander Bell Drive (O) Columbia, MD — 1,242 4,969 2,525 1,242 7,494 8,736 (3,394 ) 1990 12/31/1998 6721 Columbia Gateway Drive (O) Columbia, MD 29,252 1,753 34,090 — 1,753 34,090 35,843 (3,233 ) 2009 9/28/2000 6724 Alexander Bell Drive (O) Columbia, MD 10,939 449 5,039 579 449 5,618 6,067 (1,787 ) 2001 5/14/2001 6731 Columbia Gateway Drive (O) Columbia, MD — 2,807 19,098 1,648 2,807 20,746 23,553 (6,546 ) 2002 3/29/2000 6740 Alexander Bell Drive (O) Columbia, MD — 1,424 5,696 3,045 1,424 8,741 10,165 (3,933 ) 1992 12/31/1998 6741 Columbia Gateway Drive (O) Columbia, MD — 675 1,711 114 675 1,825 2,500 (195 ) 2008 9/28/2000 6750 Alexander Bell Drive (O) Columbia, MD — 1,263 12,461 3,351 1,263 15,812 17,075 (5,893 ) 2001 12/31/1998 6760 Alexander Bell Drive (O) Columbia, MD — 890 3,561 1,979 890 5,540 6,430 (2,582 ) 1991 12/31/1998 6940 Columbia Gateway Drive (O) Columbia, MD 17,300 3,545 9,916 3,162 3,545 13,078 16,623 (5,274 ) 1999 11/13/1998 6950 Columbia Gateway Drive (O) Columbia, MD — 3,596 14,269 1,033 3,596 15,302 18,898 (5,975 ) 1998 10/22/1998 7000 Columbia Gateway Drive (O) Columbia, MD 15,800 3,131 12,103 622 3,131 12,725 15,856 (3,246 ) 1999 5/31/2002 7015 Albert Einstein Drive (O) Columbia, MD 2,486 2,058 6,093 826 2,058 6,919 8,977 (2,179 ) 1999 12/1/2005 7061 Columbia Gateway Drive (O) Columbia, MD — 729 3,094 571 729 3,665 4,394 (1,460 ) 2000 8/30/2001 7063 Columbia Gateway Drive (O) Columbia, MD — 902 3,684 1,043 902 4,727 5,629 (2,058 ) 2000 8/30/2001 7065 Columbia Gateway Drive (O) Columbia, MD — 919 3,763 1,263 919 5,026 5,945 (1,923 ) 2000 8/30/2001 7067 Columbia Gateway Drive (O) Columbia, MD — 1,829 11,823 2,415 1,829 14,238 16,067 (4,340 ) 2001 8/30/2001 7125 Columbia Gateway Drive (L) Columbia, MD — 3,361 128 279 3,361 407 3,768 — 1973/1999(8) 6/29/2006 7125 Columbia Gateway Drive (O) Columbia, MD 33,779 17,126 46,994 6,583 17,126 53,577 70,703 (10,556 ) 1973/1999 6/29/2006 7130 Columbia Gateway Drive (O) Columbia, MD 6,519 1,350 4,359 1,784 1,350 6,143 7,493 (1,577 ) 1989 9/19/2005 7134 Columbia Gateway Drive (O) Columbia, MD 2,949 704 1,971 299 704 2,270 2,974 (499 ) 1990 9/19/2005 7138 Columbia Gateway Drive (O) Columbia, MD 5,406 1,104 3,518 1,961 1,104 5,479 6,583 (2,174 ) 1990 9/19/2005 7142 Columbia Gateway Drive (O) Columbia, MD 6,280 1,342 3,978 1,326 1,342 5,304 6,646 (1,406 ) 1994 9/19/2005 7150 Columbia Gateway Drive (O) Columbia, MD 4,850 1,032 3,429 321 1,032 3,750 4,782 (867 ) 1991 9/19/2005       Initial Cost   Gross Amounts Carried At Close of Period       Property (Type) (1) Location Encumbrances (2) Land Building and Land Improvements Costs Capitalized Subsequent to Acquisition Land Building and Land Improvements Total (3)(4) Accumulated Depreciation (5) Year Built or Renovated Date Acquired (6) 7150 Riverwood Drive (O) Columbia, MD — 1,821 4,388 972 1,821 5,360 7,181 (1,163 ) 2000 1/10/2007 7160 Riverwood Drive (O) Columbia, MD — 2,732 7,006 1,503 2,732 8,509 11,241 (2,688 ) 2000 1/10/2007 7170 Riverwood Drive (O) Columbia, MD — 1,283 3,096 594 1,283 3,690 4,973 (726 ) 2000 1/10/2007 7175 Riverwood Drive (O) Columbia, MD — 1,788 4,133 — 1,788 4,133 5,921 — 1996(7) 7/27/2005 7200 Redstone Gateway (O) Huntsville, MD — — 4,531 — — 4,531 4,531 — (7) 3/23/2010 7200 Riverwood Road (O) Columbia, MD — 4,089 16,356 3,001 4,089 19,357 23,446 (6,741 ) 1986 10/13/1998 7205 Riverwood Drive (O) Columbia, MD — 1,367 14,300 — 1,367 14,300 15,667 — (7) 7/27/2005 7272 Park Circle Drive (O) Hanover, MD 5,232 1,479 6,300 1,798 1,479 8,098 9,577 (1,663 ) 1991/1996 1/10/2007 7318 Parkway Drive (O) Hanover, MD — 972 3,888 812 972 4,700 5,672 (1,582 ) 1984 4/16/1999 7320 Parkway Drive (O) Hanover, MD 7,000 905 3,570 1,575 905 5,145 6,050 (1,557 ) 1983 4/4/2002 745 Space Center Drive (O)(10) Colorado Springs, CO — 654 7,521 15 654 7,536 8,190 (171 ) 2006 7/8/2005 7467 Ridge Road (O) Hanover, MD — 1,629 6,517 1,924 1,629 8,441 10,070 (3,346 ) 1990 4/28/1999 7700 Potranco Road (O) San Antonio, TX — 14,020 38,804 7 14,020 38,811 52,831 (5,703 ) 1982/1985 3/30/2005 7700-1 Potranco Road (O) San Antonio, TX — — 1,066 — — 1,066 1,066 (108 ) 2007 3/30/2005 7700-5 Potranco Road (O) San Antonio, TX — — 1,884 — — 1,884 1,884 (154 ) 2009 3/30/2005 7740 Milestone Parkway (O) Hanover, MD 17,548 3,825 34,363 61 3,825 34,424 38,249 (2,265 ) 2009 7/2/2007 7770 Backlick Road (O) Springfield, VA 931 6,387 71,600 8 6,387 71,608 77,995 (157 ) 2012(7) 3/10/2010 800 International Drive (O) Linthicum, MD 8,408 775 3,099 947 775 4,046 4,821 (1,662 ) 1988 4/30/1998 8000 Potranco Road (O) San Antonio, TX — 1,964 21,178 — 1,964 21,178 23,142 (1,149 ) 2010 1/20/2006 8003 Corporate Drive (O) White Marsh, MD — 611 1,611 53 611 1,664 2,275 (311 ) 1999 1/9/2007 8007 Corporate Drive (O) White Marsh, MD — 1,434 3,336 307 1,434 3,643 5,077 (727 ) 1995 1/9/2007 8010 Corporate Drive (O) White Marsh, MD — 1,349 3,262 1,672 1,349 4,934 6,283 (842 ) 1998 1/9/2007 8013 Corporate Drive (O) White Marsh, MD — 642 1,536 1,809 642 3,345 3,987 (432 ) 1990 1/9/2007 8015 Corporate Drive (O) White Marsh, MD — 446 1,116 243 446 1,359 1,805 (306 ) 1990 1/9/2007 8019 Corporate Drive (O) White Marsh, MD — 680 1,898 738 680 2,636 3,316 (555 ) 1990 1/9/2007 8020 Corporate Drive (O) White Marsh, MD — 2,184 3,767 2,199 2,184 5,966 8,150 (954 ) 1997 1/9/2007 8023 Corporate Drive (O) White Marsh, MD — 651 1,603 5 651 1,608 2,259 (267 ) 1990 1/9/2007 8030 Potranco Road (O) San Antonio, TX — 1,964 21,298 — 1,964 21,298 23,262 (1,148 ) 2010 1/20/2006 8094 Sandpiper Circle (O) White Marsh, MD — 1,960 3,716 369 1,960 4,085 6,045 (820 ) 1998 1/9/2007 8098 Sandpiper Circle (O) White Marsh, MD — 1,797 3,651 633 1,797 4,284 6,081 (558 ) 1998 1/9/2007 8100 Potranco Road (L) San Antonio, TX — 1,964 1,396 — 1,964 1,396 3,360 — (8) 6/14/2005 8110 Corporate Drive (O) White Marsh, MD — 2,285 10,117 489 2,285 10,606 12,891 (2,202 ) 2001 1/9/2007 8140 Corporate Drive (O) White Marsh, MD — 2,158 8,457 2,018 2,158 10,475 12,633 (3,046 ) 2003 1/9/2007 849 International Drive (O) Linthicum, MD 11,692 1,356 5,426 3,081 1,356 8,507 9,863 (4,043 ) 1988 2/23/1999 8621 Robert Fulton Drive (O) Columbia, MD 11,000 2,317 12,642 199 2,317 12,841 15,158 (2,314 ) 2005-2006 6/10/2005 8661 Robert Fulton Drive (O) Columbia, MD 6,200 1,510 3,764 1,042 1,510 4,806 6,316 (1,518 ) 2002 12/30/2003 8671 Robert Fulton Drive (O) Columbia, MD 7,600 1,718 4,280 1,941 1,718 6,221 7,939 (2,148 ) 2002 12/30/2003 870 Elkridge Landing Road (O) Linthicum, MD 18,900 2,003 9,442 6,689 2,003 16,131 18,134 (7,148 ) 1981 8/3/2001 881 Elkridge Landing Road (O) Linthicum, MD 11,812 1,034 4,137 1,049 1,034 5,186 6,220 (1,991 ) 1986 4/30/1998       Initial Cost   Gross Amounts Carried At Close of Period       Property (Type) (1) Location Encumbrances (2) Land Building and Land Improvements Costs Capitalized Subsequent to Acquisition Land Building and Land Improvements Total (3)(4) Accumulated Depreciation (5) Year Built or Renovated Date Acquired (6) 891 Elkridge Landing Road (O) Linthicum, MD — 1,165 4,772 1,777 1,165 6,549 7,714 (2,674 ) 1984 7/2/2001 900 Elkridge Landing Road (O) Linthicum, MD — 1,993 7,972 2,887 1,993 10,859 12,852 (4,722 ) 1982 4/30/1998 900 International Drive (O) Linthicum, MD 8,008 981 3,922 834 981 4,756 5,737 (1,964 ) 1986 4/30/1998 901 Elkridge Landing Road (O) Linthicum, MD — 1,156 4,437 1,558 1,156 5,995 7,151 (2,148 ) 1984 7/2/2001 911 Elkridge Landing Road (O) Linthicum, MD — 1,215 4,861 2,024 1,215 6,885 8,100 (2,789 ) 1985 4/30/1998 920 Elkridge Landing Road (O) Linthicum, MD — 2,081 9,683 687 2,081 10,370 12,451 (4,084 ) 1982 7/2/2001 921 Elkridge Landing Road (O) Linthicum, MD — 1,044 4,176 639 1,044 4,815 5,859 (1,989 ) 1983 4/30/1998 930 International Drive (O) Linthicum, MD 8,488 1,013 4,053 1,100 1,013 5,153 6,166 (2,203 ) 1986 4/30/1998 938 Elkridge Landing Road (O) Linthicum, MD — 1,209 4,748 476 1,209 5,224 6,433 (1,615 ) 1984 7/2/2001 939 Elkridge Landing Road (O) Linthicum, MD — 939 3,756 1,790 939 5,546 6,485 (2,452 ) 1983 4/30/1998 940 Elkridge Landing Road (L) Linthicum, MD — 1,104 4,718 170 1,104 4,888 5,992 (4,884 ) (8) 7/2/2001 9651 Hornbaker Road (D) Manassas, VA — 6,050 196,428 253 6,050 196,681 202,731 (2,809 ) 2010 9/14/2010 9690 Deereco Road (O) Timonium, MD — 3,415 13,723 5,833 3,415 19,556 22,971 (7,927 ) 1988 12/21/1999 980 Technology Court (O)(10) Colorado Springs, CO — 526 2,046 442 526 2,488 3,014 (585 ) 1995 9/28/2005 985 Space Center Drive (O)(10) Colorado Springs, CO — 777 12,287 1,569 777 13,856 14,633 (2,948 ) 1989 9/28/2005 9900 Franklin Square Drive (O) White Marsh, MD — 979 3,466 202 979 3,668 4,647 (734 ) 1999 1/9/2007 9910 Franklin Square Drive (O) White Marsh, MD 5,040 1,219 6,590 65 1,219 6,655 7,874 (1,457 ) 2005 1/9/2007 9920 Franklin Square Drive (O) White Marsh, MD — 1,058 5,293 1,429 1,058 6,722 7,780 (1,470 ) 2006 1/9/2007 9925 Federal Drive (O)(10) Colorado Springs, CO — 1,129 4,334 80 1,129 4,414 5,543 (97 ) 2008 9/28/2005 9930 Franklin Square Drive (O) White Marsh, MD — 1,137 3,921 36 1,137 3,957 5,094 (795 ) 2001 1/9/2007 9940 Franklin Square Drive (O) White Marsh, MD — 1,052 3,382 281 1,052 3,663 4,715 (732 ) 2000 1/9/2007 9945 Federal Drive (O)(10) Colorado Springs, CO — 1,854 849 — 1,854 849 2,703 (13 ) 2009 9/28/2005 9950 Federal Drive (O)(10) Colorado Springs, CO — 877 5,045 1,501 877 6,546 7,423 (1,944 ) 2001 12/22/2005 9960 Federal Drive (O)(10) Colorado Springs, CO — 695 2,286 291 695 2,577 3,272 (256 ) 2001 12/22/2005 9965 Federal Drive (L)(10) Colorado Springs, CO — 466 — — 466 — 466 — (8) 12/22/2005 9965 Federal Drive (O)(10) Colorado Springs, CO — 1,401 6,061 565 1,401 6,626 8,027 (907 ) 1983/2007 1/19/2006 999 Corporate Boulevard (O) Linthicum, MD 13,533 1,187 8,332 556 1,187 8,888 10,075 (3,230 ) 2000 8/1/1999 Aerotech Commerce (L) Colorado Springs, CO — 900 — — 900 — 900 — (8) 5/19/2006 Arborcrest (O) Blue Bell, PA — 21,969 83,529 1,094 21,969 84,623 106,592 (2,686 ) 1991(6)(7) 10/14/1997 Arundel Preserve (L) Hanover, MD — — 5,886 — — 5,886 5,886 — (8) (9) Ashburn Crossing - DC-8 (O) Ashburn, VA — 7,291 — — 7,291 — 7,291 — (7) 12/27/2012 Ashburn Crossing - DC-9 (O) Ashburn, VA — 4,192 — — 4,192 — 4,192 — (7) 12/27/2012 Ashburn Crossing (L) Ashburn, VA — 4,309 3 — 4,309 3 4,312 — (8) 12/27/2012 Canton Crossing Land (L) Baltimore, MD — 16,085 1,820 — 16,085 1,820 17,905 — (8) 10/27/2009 Canton Crossing Util Distr Ctr (O) Baltimore, MD — 7,300 15,550 722 7,300 16,272 23,572 (1,655 ) 2005 10/27/2009 Columbia Gateway - Southridge (L) Columbia, MD — 6,387 2,938 — 6,387 2,938 9,325 — (8) 9/20/2004 Dahlgren Technology Center (L) Dahlgren, VA — 1,083 178 — 1,083 178 1,261 — (8) 3/16/2005 Expedition VII (L) Lexington Park, MD — 705 726 — 705 726 1,431 — (8) 3/24/2004 Indian Head (L) Bryans Road, MD — 6,436 — — 6,436 — 6,436 — (8) 10/23/2006       Initial Cost   Gross Amounts Carried At Close of Period       Property (Type) (1) Location Encumbrances (2) Land Building and Land Improvements Costs Capitalized Subsequent to Acquisition Land Building and Land Improvements Total (3)(4) Accumulated Depreciation (5) Year Built or Renovated Date Acquired (6) InterQuest (L) Colorado Springs, CO — 14,515 8 — 14,515 8 14,523 — (8) 9/28/2005 M Square Research Park (L) College Park, MD — — 3,602 — — 3,602 3,602 — (8) 1/29/2008 National Business Park (L) Annapolis Junction, MD — 2,372 6,354 — 2,372 6,354 8,726 — (8) 11/14/2003 National Business Park North (L) Jessup, MD — 25,654 25,069 — 25,654 25,069 50,723 — (8) 6/29/2006 North Gate Business Park (L) Aberdeen, MD — 6,486 10,717 — 6,486 10,717 17,203 — (8) 9/14/2007 Northwest Crossroads (L) San Antonio, TX — 7,430 836 — 7,430 836 8,266 — (8) 1/20/2006 Old Annapolis Road (O) Columbia, MD — 1,637 5,500 2,103 1,637 7,603 9,240 (2,333 ) 1974/1985 12/14/2000 Patriot Park (L) Colorado Springs, CO — 8,768 248 — 8,768 248 9,016 — (8) 7/8/2005 Patriot Ridge (L) Springfield, VA — 18,517 10,873 — 18,517 10,873 29,390 — (8) 3/10/2010 Redstone Gateway (L) Huntsville, AL — — 13,700 — — 13,700 13,700 — (8) 3/23/2010 Route 15/Biggs Ford Road (L) Frederick, MD — 8,703 526 — 8,703 526 9,229 — (8) 8/28/2008 Sentry Gateway (L) San Antonio, TX — 8,275 3,621 — 8,275 3,621 11,896 — (8) 3/30/2005 West Nursery Road (L) Linthicum, MD — 1,441 53 — 1,441 53 1,494 — (8) 10/28/2009 Westfields - Park Center (L) Herndon, VA — 3,609 2,640 — 3,609 2,640 6,249 — (8) 7/18/2002 Westfields Corporate Center (L) Herndon, VA — 7,141 1,342 — 7,141 1,342 8,483 — (8) 7/31/2002 White Marsh (L) White Marsh, MD — 30,322 10,385 — 30,322 10,385 40,707 — (8) 1/9/2007 Woodland Park (L) Herndon, VA — 9,614 81 — 9,614 81 9,695 — (8) 4/29/2004 Other Developments, including intercompany eliminations (V) Various — 7 (152 ) (438 ) 7 (590 ) (583 ) 689 Various Various     $ 1,015,130 $ 681,001 $ 2,893,547 $ 285,412 $ 681,001 $ 3,178,959 $ 3,859,960 $ (568,176 )                             (1) A legend for the Property Type follows: (O) = Office Property; (L) = Land held or pre-construction; (D) = Data Center; and (V) = Various. (2) Excludes our term loan facilities of $770.0 million, senior exchangeable notes of $230.9 million, unsecured notes payable of $1.8 million, and net premiums on the remaining loans of $1.3 million. (3) The aggregate cost of these assets for Federal income tax purposes was approximately $3.4 billion at December 31, 2012. (4) As discussed in Note 5 to our Consolidated Financial Statements, we recognized impairment losses of $46.1 million in connection with our property in Greater Philadelphia, Pennsylvania and $19.0 million, including exit costs, in connection with certain properties included in our Strategic Reallocation Plan. (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, 2012. (8) Held or under pre-construction at December 31, 2012. (9) Development in progress in anticipation of acquisition at December 31, 2012. (10) Included in our Strategic Reallocation Plan and classified as held for sale as of December 31, 2012. The following table summarizes our changes in cost of properties for the years ended December 31, 2012, 2011 and 2010 (in thousands):             2012   2011   2010   Beginning balance     $ 4,038,932   $ 3,948,487   $ 3,452,512   Acquisitions of operating properties     33,684   26,887   187,052   Improvements and other additions     214,418   304,079   338,358   Sales     (291,491 )   (75,315 )   (29,430 )   Impairments     (121,557 )   (165,206 )   —   Other dispositions     (13,891 )   —   —   Other     (135 )   —   (5 )   Ending balance     $ 3,859,960   $ 4,038,932   $ 3,948,487                       The following table summarizes our changes in accumulated depreciation for the same time periods (in thousands):             2012   2011   2010   Beginning balance     $ 577,601   $ 503,032   $ 422,612   Depreciation expense     93,158   99,173   88,048   Sales     (40,346 )   (9,640 )   (7,764 )   Impairments     (58,855 )   (15,039 )   —   Other dispositions     (3,247 )   —   —   Other     (135 )   75   136   Ending balance     $ 568,176   $ 577,601   $ 503,032