Alexander McMennamy was born in Halifax County, Virginia on September 15, 1758. A resident of Caswell County, North Carolina, he served several tours as a private, one of which was under the command of Captain Frederick Debow in the Caswell County Regiment in 1780. He later served as a sergeant of the same regiment during the Battle of Guilford Courthouse in 1781. He may have also served as a captain in 1782. He later moved to Wilson County, Tennessee in 1810. He died there in about March 1840.