List of the United States National Park System official units

The Official Units of the National Park System of the United States is the collection of physical properties owned or administered by the National Park Service.

As of January 2017, there are 417 official units of the National Park System. However, this number can be misleading. For example, Denali National Park and Preserve are counted as two units, since the same name applies to a national park and an adjacent national preserve. Yet Jean Lafitte National Historical Park and Preserve is counted as one unit, despite its double designation. Counting methodology is rooted in the language of a park's enabling legislation. Elsewhere, Fort Moultrie National Monument is not counted as a separate unit because it is considered a feature of the larger Fort Sumter National Monument. Furthermore, the NPS contributes resources to "affiliated areas" which do not fall under its administration, and these do not count toward the official list number. An example is Oklahoma City National Memorial.

These units are a subset of the List of areas in the National Park System of the United States, and nearly all participate in the national park passport stamps program. Until 2013, Delaware was the only state without an official unit (President Barack Obama designated First State National Monument under the Antiquities Act on March 25, 2013. It was subsequently redesignated a national historical park.) National park system units are also found in Washington, D.C., Guam, American Samoa, the U.S. Virgin Islands, and Puerto Rico.

...
Wikipedia