John Fairfax was an overseer working at the Mansion House Farm from 1784 until 1790. In the fall of 1784, Fairfax agreed to work for George Washington at a salary of thirty pounds per year. The contract was renegotiated in the fall of 1785, when his salary was increased to forty pounds.1
John Fairfax was distantly related to the Fairfax family known well by George Washington who lived near Mount Vernon at Belvoir Plantation. William Fairfax, Sr. was married twice and had a total of ten children (six daughters and four sons, one of whom was Washington's overseer, John Fairfax). John Fairfax was the son of his father’s second marriage, to Virginian Elizabeth Buckner Fairfax.2
On October 26th, 1785, Washington sent Fairfax to Boston to meet a donkey and its handler, a gift to Washington from the King of Spain, in order to escort them to Virginia. Fairfax and the group from Spain left Boston on November 10, 1785 and arrived at Mount Vernon on December 5. On January 11, 1786, Washington sent Fairfax to "forwarn some persons who were hunting upon my land from the like practice." Two months later, on March 13, 1786, Washington noted that he had "Sent my Boat to Alexand[ri]a. for Salt with the Overseer in it who by my order, engaged my Fishing landing at Johnsons ferry to Mr. Lomax in Alexandria-who is to put doors and windows to the house and pay Twenty five pounds for the use of it during the fishing Season."3
In the summer of 1786, Washington sent Fairfax to Maryland to bring some sheep to Mount Vernon.4 Several months later, upon learning that some donkeys and game birds had arrived in Baltimore from the Marquis de Lafayette, Washington sent John Fairfax to retrieve the animals.
John Fairfax left Washington's employ in December of 1790 and moved to Monongalia County. There Fairfax became a justice of the peace in 1794 and later represented the county in the Virginia House of Delegates from 1809 to 1810, and again from 1814 until 1815. His first wife was a Virginian named Mary Byrne, with whom he had two sons. Fairfax later married Anne Lloyd Franklin from Charles County, Maryland, with whom he had two more children, one of whom was named George Washington Fairfax. Fairfax returned to Mount Vernon at least once. On November 2nd, 1799, only about a month before George Washington died, he noted in his diary that "Mr. Jno. Fairfax (formerly an overseer of mine) came here before dinner and stayed all Night."5