John Semple (d. 1773) was a Scottish speculator who moved from Charles County, Md., to Prince William County, Va., in 1763 and took over the iron furnace and gristmills on Occoquan Creek that John Ballendine had previously operated. About that same time, Semple acquired Keep Triste iron furnace, on the Virginia shore of the Potomac River a short distance above Harpers Ferry, and in May 1765 he bought from Thomas Colvill the tract of land called Merryland lying in nearby Frederick County, Md. (skaggs description begins David C. Skaggs and Richard K. MacMaster, eds. “Post-Revolutionary Letters of Alexander Hamilton, Piscataway Merchant.” Maryland Historical Magazine 63 (1968): 22–54; 65 (1970): 18–35. description ends , 63:28 n.15). He was also an active promoter of a scheme to improve the navigation of the Potomac by forming a company to build locks around the falls and probably discussed the idea with GW on this visit (Semple to GW, 8 Jan. 1770, MnHi).