He was the son of George W. Fairfax and Isabella McNeill (AMW's sister).
He entered the US navy as midshipman from North Carolina, and made the cruise around the world on the Columbia, 1838-40, and again in 1845-47 under Commodore Biddle. He was on the California coast during the Mexican war, and was one of the party that captured William Walker the filibuster. He commanded Greytown, Nicaragua, 1858. He was eventually made Rear-Admiral in 1880. Donald M. Fairfax, shared his flat in Baltimore with AMW when the latter was in financial need in 1855.
The Twentieth Century Biographical Dictionary of Notable Americans, vol. 4, p. 36; Who Was Who in America, Chicago, 1963, p. 175; The List of Officers of the Navy of the USA 1775-1900, New York, 1901, vol. 2, p. 188.