John Mann Sr. served in the Virginia Militia during the Revolutionary War and later took on the role of captain in the Ohio Militia.
In around 1801, John, along with his wife Susannah and their family, joined their eldest son, John Jr., in Miami County, Ohio.
At that time, John Sr. appointed his son-in-law, Andrew Hatfield, as the agent to sell his Virginia land holdings. , This action cemented the Mann family's mid-west roots.
After spending several years in Ohio with his sons, John and Susannah eventually relocated to Delaware County, Indiana.