John Hanson Thomas III was born around 1841 in Baltimore, Maryland, to John Hanson Thomas and Annie Campbell Gordon. His father was a bank president who owned $100,000 of real estate and $300,000 of personal property by 1860. He grew up and attended school in Baltimore, and he attended the University of Maryland’s preparatory department in the late 1850s. He served in the Confederate army during the Civil War. He returned to Baltimore after the war, and he earned a living as a merchant. He married Mary Howard Beirne on October 16, 1866. He died sometime after 1870.