The Great Plains of the United States ...the vast prairie... was once called the "Great American Desert." Most of the states found among the Plains States were part of the 1803 Lousiana Purchase.
Map courtesy Southern Missouri State University
Through the early part of the 19th century (1800-1899) easterners and immigrants mostly from Europe settled the plains states or trekked through them towards the west. Generally, the settlers traveled by river as far as they could and then set about land crossings on covered wagon trains. That generally meant they got as far as St. Louis or Kansas City before setting out on the trails in thier covered wagons.