- Abraham Lincoln Birthplace National Historic Site@ (1)
- Acadia National Park@ (10)
- Adams National Historic Park@ (1)
- Agate Fossil Beds National Monument@ (1)
- Alagnak Wild River@ (1)
- Alibates Flint Quarries National Monument@ (1)
- Allegheny Portage Railroad NHS@ (1)
- Amistad National Recreation Area@ (1)
- Andersonville National Historic Site@ (1)
- Andrew Johnson National Historic Site@ (2)
- Aniakchak National Monument@ (1)
- Antietam NB@ (1)
- Apostle Islands National Lakeshore@ (1)
- Appalachian National Scenic Trail (21)
- Appomattox Courthouse NHP@ (1)
- Arches National Park@ (8)
- Arlington House@ (2)
- Assateague Island NS@ (3)
- Aztec Ruins NM@ (3)
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