Noatak National Preserve, 6,569,904 acres (2,660,811 hectares), N Alaska. The preserve is the largest mountain-ringed river basin in the United States that is still virtually unaffected by human activities. It is a transition zone for plants and animals between arctic and subarctic environments and includes the Grand Canyon of the Noatak River. Proclaimed a national monument in 1978, it was designated a national preserve in 1980. The 330-mi (531-km) Noatak Wild River, authorized in 1980, lies partially within the preserve and partially in the Gates of the Arctic National Park and Preserve. See National Parks and Monuments (table).