Creation of the program
Prior to 1935, efforts to preserve cultural heritage of national importance were made by piecemeal efforts of the United States Congress. In 1935, Congress passed the Historic Sites Act, which authorized the Interior Secretary authority to formally record and organize historic properties, and to designate properties as having "national historical significance", and gave the National Park Service authority to administer historically significant federally owned properties. Over the following decades, surveys such as the Historic American Buildings Survey amassed information about culturally and architecturally significant properties in a program known as the Historic Sites Survey. Most of the designations made under this legislation became National Historic Sites, although the very first designation, made December 20, 1935, was for a National Memorial, the Gateway Arch National Park (then known as the Jefferson National Expansion Memorial) in St. Louis, Missouri. The first National Historic Site designation was made for the Salem Maritime National Historic Site on March 17, 1938.
In 1960, the National Park Service took on the administration of the survey data gathered under this legislation, and the National Historic Landmark program began to take more formal shape. When the National Register of Historic Places was established in 1966, the National Historic Landmark program was encompassed within it, and rules and procedures for inclusion and designation were formalized. Because listings (either on the National Register, or as an NHL) often triggered local preservation laws, legislation in 1980 amended the listing procedures to require owner agreement to the designations.
On October 9, 1960, 92 properties were announced as designated NHLs by Secretary of the Interior Fred A. Seaton. The first of these was a political nomination: the Sergeant Floyd Monument in Sioux City, Iowa was officially designated on June 30 of that year, but for various reasons, the public announcement of the first several NHLs was delayed.