Is it true that the prison break was filmed in prison?

First of all, it is clear that the prison break was filmed in prison. Fox River State Prison mentioned in the TV series is the first prison that the protagonist entered in Prison Break.

Fox River Prison is actually Joliet Correctional Center (prison) in Joliet, Illinois. This Victorian building was built in 1858 and was designed by William Boynton, the architect of the Chicago Water Tower. The prison was closed in 2002 and is now used as the scene of Prison Break. Even if the prison is closed now, there are still guards.

Note: Some shots involved in general movies are basically from real scenes, but they are not put into use now.