The system of parks, monuments, memorials, historical parks, seashores and other designations under the National Park Service now includes 398 units. (There are also a number of national monuments administered by other federal agencies, foremost the Bureau of Land Management.)
Of the 398 NPS units, 59 are designated national parks — “generally large natural places having a wide variety of attributes, at times including significant historic assets” — America’s foremost natural treasures.
The year indicates when the park was established or when an existing area was re-designated as a national park. A few parks — e.g., Yellowstone, Great Smoky Mountains — are in more than one state.