The Rio Grande almost equally divides this semiarid landscape with the United States on the north side of the river and Mexico on the south. The outline of the border towns of Laredo (United States) and Nuevo Laredo (Mexico) are barely discernible where the river makes a sharp course change from south to east. Much of the dry region consists of sandy soils derived from underlying sandstone rocks. Land ownership boundaries provide distinctive field patterns on both sides of the U.S.-Mexico border.