Fort Buttermilk was a French and Indian War fortification constructed by Capt. Thomas Waggener's Virginia Regiment Company in spring 1756 to protect the settlers living along the South Branch of the Potomac south of present Moorefield, Hardy County. Col. George Washington, commander of the Virginia Regiment, noted, "since numbers of the Inhabitants…are lately moved down about…a place called Butter-milk Fort, which renders…it necessary to place the troops, or at least a principal part of them, there also to protect the Inhabitants in sowing and gathering their Crops, Etc." During much of the French and Indian War this fort usually had a garrison of between 28 and 70 Virginia Regiment soldiers (mostly from Waggener's company) as well as militiamen. No description of this fort has been found, but it was likely a bastioned wooden stockade.

In April or May 1756, 16 to 18 men from Fort Buttermilk and Fort Pleasant left the latter fort to pursue an Indian raiding party sighted near Fort Pleasant. These soldiers or militia were soundly defeated with the loss of seven men killed and four wounded by the Delaware and Shawnee Indians under Killbuck at what is known as the Battle of the Trough. In October 1757 another Indian raiding party killed two men near Fort Buttermilk. After the burning of Fort Duquesne (later Pittsburgh) in late 1758, Fort Buttermilk is no longer mentioned in historical documents and was probably abandoned. The origin of this fort's name is unknown, although as historian William Ansel relates, "One story would have us believe that at the time the fort was being constructed, a party of Indians ventured into the area and so harassed the cows about the place that at milking time, they gave buttermilk instead of the standard variety."