OKLAHOMA CITY (AP) — It's been 40 years since inmates rioted at the Oklahoma State Penitentiary at McAlester — one of the most destructive prison riots in American history. The prison erupted into violence on July 27, 1973, the result of overcrowding, inadequate supervision, poor health care and a culture of violence within the prison walls. When rioting ended three days later, three inmates had been killed by other inmates, more than 20 correctional officers and inmates were injured and a dozen buildings had burned to the ground. The prison was eventually rebuilt as a maximum security prison. Jerry Massie, public information officer for the Department of Corrections, says the riot forced state leaders and correctional officials to change the way the state's prisons operated. Training improved for correctional officers and other prison staffers. Copyright 2013 The Associated Press.