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Maryland Historic Site
The spot two miles south of Oldtown, Md., is where the North Branch and the South Branch of the Potomac meet (canal milepost 165). Surveyors here decided that the North Branch appeared to have a greater flow of river and was therefore considered longer. The fact that the South Branch was a longer river was discovered in 1754, when Thomas Cresap surveyed the sources of the river. Cresap also verified that the source of the South Branch was farther west than the source of the North Branch. Since the original land grant allowed Maryland to claim ownership to the "first fountain" of the Potomac, using the source of the South Branch as the basis for the state boundary would have given Maryland considerably more land. By 1754, however, the Fairfax Stone, at the source of the North Branch, was considered to be the source of the Potomac. Virginia was insistent that the Fairfax Stone remain as the marker for the boundary of Maryland.