McMath was the son of Joseph and Elizabeth Wilshire McMath of Georgia. He married the former Frances Gorman and had eight children between 1815 and 1838: Lucanda, Jerusha, Joseph Washington, William, James Hillman, Sarah Elizabeth "Bessie", Elisha Jr, and Clement Clay.
McMath's home was used as a polling place in 1827 and as a post office (with McMath as postmaster) in 1842. In the 1850s, writer Mary Gordon Duffee described McMath's homestead as having a "big roomy house and fine spring".
- Brown, Virginia Pounds and Jane Porter Nabers, eds. (1970) Mary Gordon Duffee's Sketches of Alabama. Tuscaloosa: University of Alabama Press ISBN 081735011X