During the nomination process, the property is evaluated in terms of the four criteria for inclusion on the National Register of Historic Places.

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.

[4] 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.

[6] 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 Federal Office of Archaeology and Historic Preservation (OAHP).

[4] During the Register's earliest years in the late 1960s and early 1970s, organization was lax and SHPOs were small, understaffed and underfunded.

[8] From 1978 until 1981, the main agency for the National Register was the Heritage Conservation and Recreation Service (HCRS) of the United States Department of the Interior.

[8] Although not described in detail in the 1966 act, SHPOs eventually became integral to the process of listing properties on the National Register.

[6][10] It is hereby declared to be the policy of the United States Government that special effort should be made to preserve the natural beauty of the countryside and public park and recreation lands, wildlife and waterfowl refuges, and historic sites.

[11] Any individual can prepare a National Register nomination, although historians and historic preservation consultants often are employed for this work.

The nomination consists of a standard registration form (NPS 10-900) and contains basic information about a property's physical appearance and the type of significance embodied in the building, structure, object, site, or district.

[13] Information about architectural styles, association with various aspects of social history and commerce and ownership are all integral parts of the nomination.

Each nomination contains a narrative section that provides a detailed physical description of the property and justifies why it is significant historically with regard either to local, state, or national history.

[15][16] There is a misconception that there is a strict rule that a property must be at least 50 years old to be listed in the National Register of Historic Places.

John H. Sprinkle Jr., deputy director of the Federal Preservation Institute, stated:[14] [T]his "rule" is only an exception to the criteria that shape listings within the National Register of Historic Places.

[17] Examples of MPS include the Lee County Multiple Property Submission, the Warehouses in Omaha, the Boundary Markers of the Original District of Columbia and the Illinois Carnegie Libraries.

Section 106 requires the federal agency involved to assess the effect of its actions on historic resources.

The director of said agency is required to "take into account the effect of the undertaking" on the National Register property, as well as to afford the ACHP a reasonable opportunity to comment.

[20][21] In cases where the ACHP determines federal action will have an "adverse effect" on historic properties, mitigation is sought.

[21] The more general language has allowed more properties and parklands to enjoy status as protected areas by this legislation, a policy developed early in its history.

The United States Supreme Court ruled in the 1971 case Citizens to Preserve Overton Park v. Volpe that parklands could have the same protected status as "historic sites".

The term building, as in outbuilding, can be used to refer to historically and functionally related units, such as a courthouse and a jail or a barn and a house.

Sites are the locations of significant events, which can be prehistoric or historic in nature and represent activities or buildings (standing, ruined, or vanished).

Examples of types of sites include shipwrecks, battlefields, campsites, natural features and rock shelters.

Indirect protection is possible, by state and local regulations on the development of National Register properties and by tax incentives.

The National Park Service was given the responsibility to ensure that only rehabilitations that preserved the historic character of a building would qualify for federal tax incentives.

[19] The tax incentives program is operated by the Federal Historic Preservation Tax Incentives program, which is managed jointly by the National Park Service, individual State Historic Preservation Offices and the Internal Revenue Service.

[4] Essentially, this made the Landmarks a kind of "honor roll" of the most significant properties of the National Register of Historic Places.

In 2022, the U.S. has about 94,000 NRHP-listed properties, including historic districts; the total number of buildings covered is much larger.