Located about 62 miles (100 km) off the western state of Nayarit, the Islas Marias became a prison in 1905 under dictator Porfirio Diaz and was in almost constant use until it was closed by Lopez Obrador in 2019.
The penitentiary once housed many political prisoners, including Jose Revueltas, an influential Mexican writer imprisoned several times for his left-wing activism.