Reports on the Construction of the Piers of the Aqueduct of the Alexandria Canal across the Potomac River at Georgetown, District of Columbia, 1835-1840
- 1873 reprint of engineering reports on the aqueduct construction. Digitized full text of the 1873 edition (49 pages) from Google Books.
- http://books.google.com/books?vid=OCLC00856133&id=DQJ9g5Vbt7gC

Office of Planning: Historic Preservation Design Guidelines
- Guidelines on historic building alterations and maintenance. PDF files.
- http://www.planning.dc.gov/planning/cwp/view,a,1284,q,570650.asp

Intricate Details: Dupont Circle Architecture Photography Project
- Photographs of architectural details of buildings in the Dupont Circle area.
- http://www.globalmosaics.com/intricatedetails.htm

Adolf Cluss
- German-born, he became the most influential architect in Washington, DC, in the late 19th century. Includes biography, photos and information on a centenary exhibition and other events planned in 2005. English and German.
- http://www.adolf-cluss.org/

Emporis: Washington
- Focusing on city architecture, especially tall buildings (over 12 stories tall), this site has basic facts and data on notable structures in the DC metro area, searchable by building name, type or locality.
- http://www.emporis.com/en/wm/ci/?id=101047

Great Buildings Online: Architecture of Washington, DC
- Basic information on notable structures and their architects, with photos, commentary and bibliography.
- http://www.greatbuildings.com/places/dc.html

National Register Travel Itinerary
- Virtual tour of historic buildings via clickable map or list from the National Parks Service. Photographs and histories with visitor information.
- http://www.cr.nps.gov/nr//travel/wash/