<P> Because of its unique history , many of the boundaries of the political divisions of the United States were artificially constructed ( rather than being permitted to evolve and drawn using natural features of the landscape ) . Therefore , many U.S. states have straight lines as boundaries , especially in the West . However , there are a number of states , particularly in the Midwest , North and South with at least partial river borders . </P>
in which part of the u.s. is the majority of state boundaries based upon natural features
Midwest North North