National memorial is a designation in the United States for an officially recognized area that memorializes a historic person or event. As of September 2020 the National Park Service (NPS), an agency of the Department of the Interior, owns and administers 31 memorials as official units and provides assistance for 5 more, known as affiliated areas, that are operated by other organizations. Congress has also designated twenty-two additional independently operated sites as national memorials. Another five memorials have been authorized and are in the planning stage. Memorials need not be located on a site directly related to the subject, and many, such as the Lincoln Memorial, do not have the word "national" in their titles. There is a degree of overlap in development of some areas designated as memorials, monuments, and historic sites, and their characterization is not always consistent with their names, such as whether the site is closely associated with whom it memorializes.
The earliest and perhaps most recognizable is the uniquely designated Washington Monument, which was completed in 1884 and transferred to the NPS in 1933. The most recently established is the Dwight D. Eisenhower Memorial, dedicated in 2020. The Pearl Harbor National Memorial was created out of the World War II Valor in the Pacific National Monument in 2019 and was previously just the USS Arizona Memorial. The NPS national memorials are in 15 states and the District of Columbia. Washington, D.C., has the most, twelve, followed by Pennsylvania and New York, each with three. The affiliated areas are in four states (two additional beyond those with NPS memorials) and the Northern Mariana Islands, while the other sites are in nine states (five additional), the District of Columbia, and Midway Atoll. Creation of new memorials in Washington, D.C. is governed by the Commemorative Works Act, while outside the District there are no systematic regulations.