The Great Plains were long inhabited by Native Americans, who hunted the teeming herds of buffalo (see bison) that roamed the grasslands and, due to wholesale slaughter by settlers and the U.S. army, were nearly extinct by the end of the 19th cent. The region was explored by the Spanish in the 17th cent. Until well into the 19th cent., the central Great Plains were called the Great American Desert. The first westward-bound pioneers bypassed the Great Plains. The railroads were largely responsible for their development after the Civil War. An initial wave of settlement was followed by emigration in times of drought. By the mid-1930s, decades of overgrazing and poor soil management in many of the Plains states had resulted in dust storms and the devastation of crops (see Dust Bowl).