In September of 1896, 150 inmates were brought to the Ohio State Reformatory to serve their sentences. What they weren’t aware of, is that much of the prison was unfinished at the time, and the inmates would be tasked with finishing the construction. They would go on to install the sewer system, 6 outbuildings as well as a 25 foot stone wall. The reformatory’s history quickly turned dark with over 200 confirmed deaths on the property, and this led to it becoming what is known as the most haunted place in Ohio.

Sources: 

•  https://en.m.wikipedia.org/wiki/Ohio_State_Reformatory
• https://destinationmansfield.com/venue/ohio-state-reformatory-2/
• https://www.travelchannel.com/shows/ghost-adventures/articles/ohio-reformatorys-haunted-history
• https://abandonedonline.net/location/ohio-state-reformatory/
• https://www.mrps.org
• Ohio State Reformatory – Ohio Exploration Society
• Mansfield Prison (aka Ohio State Reformatory), Mansfield OH | Haunted Rooms America