List of areas in the National Park System of the United States

The National Park System of the United States is the collection of physical properties owned or administered by the National Park Service. This includes all areas designated National Parks and most National Monuments, as well as several other types of protected areas of the United States.

As of 2007, there are 391 "units" of the National Park System. However, this number is somewhat misleading. For example: Denali National Park and Preserve is counted as two units, whereas Fort Moultrie National Monument is not counted as a unit because it is considered a feature of Fort Sumter National Monument.

In addition to areas of the National Park System, the National Park Service also provides technical and financial assistance to several "affiliated areas" authorized by Congress. Affiliated areas are marked on the lists below.

The National Register of Historic Places is administered by the Park Service (with nearly 79,000 entries) and automatically includes all National Park System areas designated due to their historic significance. This includes all National Historical Parks/Historic Sites, National Battlefields/Military Parks, National Memorials, and some National Monuments.

Delaware is the only state without a unit of the park system. Units are also found in Washington, D.C., Guam, American Samoa, the U.S. Virgin Islands, and Puerto Rico.

Nearly all units managed by the National Park Service participate in the National Park Passport Stamps program.