Eastern State Penitentiary was opened in 1829, and it became a model for prisons around the world. More than 300 prisons have copied Eastern State's "radial" floor plan, with cell blocks branching out from a central hub (where a few guards can monitor all the cell blocks at once). It also pioneered the idea of a true "penitentiary", where prisoners were kept in solitude and encouraged to reflect on their wrongs.
The prison operated for 142 years, and shut down in 1971. It was opened for tours in 1994.
