Abraham Barnes (died c.1778) resided for many years in St. Mary's County, Maryland. He was a merchant, who held several public offices. Barnes was also engaged for a time in military service, attaining the rank of major by 1751, and that of colonel by 1756.  Barnes represented St. Mary's County in the Maryland legislature for a few years, and held a number of local offices, including justice and trustee of St. Mary's County Free School (see Biog. Dict. of the Maryland Legislature, 1:114-15).

In 1772, GW paid Barnes for a horse purchased by Dr. James Craik from Barnes's son John (see Ledger B, 60).