Keystone was the second iron furnace constructed in Jackson County, and the only one located in Bloomfield Township. Most of the iron was shipped down Raccoon Creek on boats when the water was high. Several men died while attempting to navigate the creek, due to the heavy load and mill dams obstructing the current. The lack of a railroad forced the men to ship the iron by wagon when the water was low.

In 1850, this iron furnace was purchased by the Green, Benner & Company. In 1861, they shut it down due to the Civil War. An Officer at Keystone named Wendall Churchill led the organization of the first company of men in Jackson County. Their regiment became the 27th at Camp Chase, which officially became Company E of the 27th Ohio Volunteer Infantry. A few other employees were also involved, including: Samuel Thomas, Charles W. Greene, and John A. Evans. A total of 232 men from Bloomfield Township fought in battle. Churchill went on to become a General and Samuel Thomas became a Colonel.

The operation at Keystone resumed when the surviving men returned in 1863. Those men instituted the first bean dinner in southern Ohio, here at Keystone Furnace. It was a memorial of their hard service, and to those that lost their life. This occurred annually while the men were alive. It eventually became a homecoming, and people would travel hundreds of miles just to attend.

Not only is the Keystone Furnace rich in history, it's also a very unique structure. The contractors carved it out of a solid sandstone cliff. Pick marks are clearly visible on the interior walls. The tunnels really set Keystone apart from the other iron furnaces in Ohio.