American Landscape and Architectural Design, 1850-1920 is a collection of about 2,800 digitized lantern slide views of American buildings and landscapes. Includes views of cities, buildings, parks, estates, gardens, with some maps and plans, including works by Frederick Law Olmsted, Jr. Bremer Pond and James Sturgis Pray, et al. There is a special section on Harvard University buildings.
Historic American Buildings Survey/Historic American Engineering Record/Historic American Landscapes Survey offers measured drawings, large-format photographs, and written histories for more than 43,000 historic structures and sites dating from Pre-Columbian times to the twentieth century.
RIBApix offers images from the British Architectural Library collections.
Digital Archive of European Architecture (Boston College)