William Triplett (1730–1803) lived at Round Hill, about four miles northwest of Mount Vernon. In 1758, when GW was having extensive repairs and improvements made on his mansion house and outbuildings at Mount Vernon, Triplett, who furnished labor and materials for construction of many of the buildings in the lower part of Fairfax County, was employed to do the brickwork and plasterwork (see Ledger A, 72). In 1760 Triplett built two dependencies in front of the mansion house. Prior to the Revolutionary War, Triplett was a frequent foxhunting companion of GW's. Triplett was the elder son of Thomas (d. 1737) and Sarah Harrison Triplett (1708–1785). After his father's death, his mother married John Manley, and among her children by this second marriage were Penelope Manley French, Sarah Manley Little, and Harrison Manley. William was later one of the executors of his half brother Harrison's estate. In September 1786, GW secured from Triplett a 142-acre tract of land on the southwestern part of Mount Vernon Neck that Manley had owned and that belonged to his estate. GW gave a bond for £426 for the land (see Ledger B, 29).

GW needed a small piece of land owned by Triplett which bordered on GW’s tumbling dam and millrace. He proposed to give Triplett some small strips of land in exchange. The negotiations had gone on for years because of boundary disputes and GW’s long absence during the war. Some of the land GW was leasing to Lund Washington was also involved in the dispute. On 18 May 1785 a deed was signed giving Triplett 29 acres on the northwest side of the millrace. The acreage involved was part of land GW had bought from George Ashford and Simon Pearson, and also a small strip of wasteland granted him in 1771. In return, Triplett gave GW 26 acres on the lower, or east, side of the millrace with 5s. token fee.