The northern cornerstone of a chain of forts built by Virginia to protect frontier settlers from Indian forays during the French and Indian War, Fort Maidstone was built on the south side of the Potomac River opposite present Williamsport, Maryland. The fort was built on the farm of Evan Watkins near his ferry, Maidstone, on the main road connecting central Virginia, Maryland, and Pennsylvania.

During the fall of 1755 and spring of 1756, Watkins's farm served as an outpost and depot for the Virginia Regiment. On May 8, 1756, George Washington directed Capt. Robert Stewart to fortify Maidstone as feasible with available tools. Later, on July 3, Stewart informed Washington that the fort consisted of entrenchments with adjacent high ground and a guardhouse. This fort was never directly assaulted by Indians but several settlers were killed nearby. Mason and Dixon stopped by on July 3, 1765, while surveying their famous line between Maryland and Pennsylvania and stated in their journal that the fort was composed of logs. This suggests that the original fort had been remodeled or completely replaced at some point between May 1756 and July 1765.