A prison cell block is seen following a tour by US President Barack Obama at the El Reno Federal Correctional Institution in El Reno, Oklahoma, July 16, 2015. Obama is the first sitting US President to visit a federal prison, in a push to reform one of the most expensive and crowded prison systems in the world. AFP PHOTO / SAUL LOEB (Photo credit should read SAUL LOEB/AFP/Getty Images)
