The Rocky Mountain Front is an area extending over 100 miles (160 km) from the central regions of the U.S. state of Montana to southern Alberta, Canada. Here, the Rocky Mountains meet the Great Plains in an abrupt altitude rise of between 4,000 to 5,000 feet (1,219–1,524 m). The Lewis Overthrust pushed eastward and over younger aged rocks, creating the Lewis Range. Also referred to as the "Crown of the Continent", the region is characterized by an uncommon ecosystem in which prairie and Northern Rockies flora and fauna overlap. The majority of the Rocky Mountain Front lies in Waterton Lakes National Park in Alberta, and Glacier National Park, Lewis and Clark National Forest as well as on private lands and the Blackfeet Indian Reservation, all of which are in Montana. The U.S. Bureau of Land Management also manages portions of the region. All of the original animal species encountered when the Lewis and Clark Expedition passed through the region still exist in their wild state, with the exception of the Bison, which lives in the wild south and west of the front, but in the area itself is represented by domesticated herds. This is one of the few places in the lower 48 states in which the Grizzly bear still ventures onto the Great Plains. Conservationists have been actively working to protect the region from oil and gas exploration interests.