During the 1930s, northwestern Oklahoma went through a period of time called the Dust Bowl. The area had little rainfall and high temperatures. This caused thousands of farmers to go into poverty and forced them to move to other parts of the United States. From 1930 to 1950, the state saw its only loss in population. It lost 6.9 percent of the people who lived there. Because of the Dust Bowl, the state made hundreds of reservoirs and man-made lakes. By the 1960s, more than 200 man-made lakes had been made. This is the most in the United States.