Heritage Documentation Programs (HDP), part of the National Park Service, administers HABS (Historic American Buildings Survey), the Federal Government's oldest preservation program, and companion programs HAER (Historic American Engineering Record), HALS (Historic American Landscapes Survey), and CRGIS (Cultural Resources Geographic Information Systems). Documentation produced through the programs constitutes the nation's largest archive of historic architectural, engineering and landscape documentation. Records on nearly 40,000 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. CRGIS data, maps and GIS applications are available at parks, battlefields, and other historic sites. HDP also develops and maintains the Secretary of the Interior's Standards and Guidelines for Architectural and Engineering Documentation, and the National Geospatial Data Standards for Cultural Resources.

HDP conducts a nationwide documentation program in partnership with state and local governments, private industry, professional societies, universities, preservation groups, and other Federal agencies. The program assigns highest priority to sites of national significance that are in danger of demolition or loss by neglect, and to National Park Service properties. In addition to the summer recording program, documentation enters the Collection through mitigation activities under appropriate sections of the National Historic Preservation Act of 1966, submissions in prize competitions, and donations. The CRGIS Facility augments this nationwide documentation program by adapting GIS and GPS technologies to traditional activities of conducting survey, maintaining historic inventories, and undertaking documentation efforts. In support of these activities the CRGIS Facility provides leadership in developing, advancing, and disseminating GPS data dictionaries, GIS applications, training courses, and spatial and metadata standards for cultural resources. CRGIS is the NPS lead program to fulfill the NPS role under OMB Circular A-16 i.e. to develop the national spatial dataset for cultural resources.

Documentation provides a permanent record of the nation's most important historic sites and large-scale objects. The Collection is unique in the strong support it enjoys from its institutional sponsors and the public, and is distinguished in its national scope, consistent format, archival stability, and continued growth. The documentation also contributes to wider recognition and appreciation of historic resources as National Historic Landmarks; provides baseline documentation for rehabilitation and restoration; and makes available well-researched materials for interpretation and illustration. Not surprisingly, it is the most heavily-used collection at the Library of Congress' Division of Prints and Photographs. By converting traditional documentation products into digital products through GIS and GPS, additional opportunities for using the information are leveraged in the arenas of land use planning, ongoing site management, and continued inventorying and monitoring.