The American frontier comprises the geography, history, folklore, and cultural expression of life in the forward wave of American expansion that began with English colonial settlements in the early 17th century and ended with the admission of the last mainland territories as states in 1912. "Frontier" refers to a contrasting region at the edge of a European-American line of settlement. American historians cover multiple frontiers but the folklore is focused primarily on the conquest and settlement of Native American lands west of the Mississippi River, in what is now the Midwest, Texas, the Great Plains, the Rocky Mountains, the Southwest, and the West Coast.