The Heritage Documentation Programs administers HABS (Historic American Buildings Survey), the Federal Government's oldest preservation program, and companion programs HAER (Historic American Engineering Record) and HALS (Historic American Landscapes Survey).
Documentation produced through the programs constitutes the nation's largest archive of historic architectural, engineering and landscape documentation. Records on nearly 45,000 historic sites, consisting of large-format, black and white photographs, measured drawings, and written historical reports, are maintained in a special collection at the Library of Congress, available to the public copy-right free in both hard copy (in the Library of Congress) and electronic (via the Web) formats.