The park covers 7,383 mi² (19,122 km²), being roughly the size of Wales. Most of this is a designated wilderness area, including 5,288 mi² (13,696 km²) of the park. The park is named after Mount Katmai, its centerpiece stratovolcano.
Established on December 2, 1980, the park is located on the Alaska Peninsula, across from Kodiak Island, with headquarters in nearby King Salmon, about 290 air miles southwest of Anchorage. Originally, on September 24, 1918, the area was designated a national monument to protect the area around the major 1912 volcanic eruption of Novarupta, which formed the Valley of Ten Thousand Smokes, a forty square mile (100 km²), 100 to 700 foot deep pyroclastic flow.
Activities at Katmai include hiking, backpacking, camping, backcountry skiing, fishing, kayaking, boat tours, and interpretive programs. There are at least fourteen active volcanoes within the national park, most recently Fourpeaked Volcano, which became active September 17, 2006 after more than 10,000 years of dormancy. This park contains numerous archaeological sites which indicate a long history of prehistoric occupations from the Paleoarctic tradition up to the Thule tradition.