Mid-20th Century

The return of normal rainfall and the heavy demand for food during World War II helped to revive agriculture The war also increased the demand for petroleum products and helped to build up a great industry based on oil. In 1959 a helium-extraction plant was opened at Keyes. Several dam-reservoir projects were begun before the war. The Grand River, or Pensacola, Dam was completed in 1941; the Denison Dam on the Red River in 1944. Many more were constructed in the postwar period.

Work on the Arkansas River Navigation System, an inland waterway system providing barge transportation from Tulsa to the Gulf of Mexico, was completed in 1971. Major Oklahoma dams that are part of this project are Eufaula, on the Canadian River; Oologah, on the Verdigris; and Robert S. Kerr, on the Arkansas. The project brought many benefits to northeastern Oklahoma, including increased hydroelectric power and recreational facilities.

Political scandals rocked the state in the 1970's and 1980's. Several high-ranking state and local officials, including Governor David Hall, were convicted of crimes. In the 1980's, the economy suffered from a recession in the oil industry and depressed farm prices. By the early 1990's, the economy had stabilized, with less dependence on agricultural and oil production. In 1995 right-wing extremists bombed the federal building in Oklahoma City, killing 168 persons.