The passage of the National Historic Preservation Act (NHPA) in 1966 established the National Register and the process for adding properties to it. Of the more than one million properties on the National Register, 80,000 are listed individually. The remainder are contributing resources within historic districts.
For most of its history the National Register has been administered by the National Park Service (NPS), an agency within the United States Department of the Interior. Its goals are to help property owners and interest groups, such as the National Trust for Historic Preservation, coordinate, identify, and protect historic sites in the United States. While National Register listings are mostly symbolic, their recognition of significance provides some financial incentive to owners of listed properties. Protection of the property is not guaranteed. During the nomination process, the property is evaluated in terms of the four criteria for inclusion on the National Register of Historic Places. The application of those criteria has been the subject of criticism by academics of history and preservation, as well as the public and politicians.
Occasionally, historic sites outside the country proper, but associated with the United States (such as the American Embassy in Tangiers) are also listed. Properties can be nominated in a variety of forms, including individual properties, historic districts, and multiple property submissions (MPS). The Register categorizes general listings into one of five types of properties: district, site, structure, building, or object. National Register Historic Districts are defined geographical areas consisting of contributing and non-contributing properties. Some properties are added automatically to the National Register when they become administered by the National Park Service. These include National Historic Landmarks (NHL), National Historic Sites (NHS), National Historical Parks, National Military Parks/Battlefields, National Memorials, and some National Monuments. (Federal properties can be proclaimed National Monuments under the Antiquities Act because of either their historical or natural significance. They are managed by multiple agencies. Only monuments that are historic in character and managed by the National Park Service are listed administratively in the National Register.)
On October 15, 1966, the Historic Preservation Act created the National Register of Historic Places and the corresponding State Historic Preservation Offices (SHPO). Initially, the National Register consisted of the National Historic Landmarks designated before the Register's creation, as well as any other historic sites in the National Park system. Approval of the act, which was amended in 1980 and 1992, represented the first time the United States had a broad-based historic preservation policy. The 1966 act required those agencies to work in conjunction with the SHPO and an independent federal agency, the Advisory Council on Historic Preservation (ACHP), to confront adverse effects of federal activities on historic preservation.
To administer the newly created National Register of Historic Places, the National Park Service of the U.S. Department of the Interior, with director George B. Hartzog Jr., established an administrative division named the Office of Archeology and Historic Preservation (OAHP). Hartzog charged OAHP with creating the National Register program mandated by the 1966 law. Ernest Connally was the Office's first director. Within OAHP new divisions were created to deal with the National Register. The division administered several existing programs, including the Historic Sites Survey and the Historic American Buildings Survey, as well as the new National Register and Historic Preservation Fund.