North Park is a broad high mountain basin in north-central Colorado, the northernmost of the state’s three great parks and the headwaters region of the North Platte River. Ringed by the Medicine Bow, Never Summer, Rabbit Ears, and Park ranges, it has long been accessed through passes that serve as mountain gateways. Walden is its main settlement, and the Illinois River valley includes the Arapaho National Wildlife Refuge. Geologically, the basin contains Mesozoic sedimentary rocks, fossils from an ancient shallow sea, and Cretaceous formations that support oil and gas production. Ranching has long dominated its economy, while wildlife changes, a failed 1914 cooperative city plan, and a link to South Park add to its history.