From Ohio History Central
Fort Dunmore was a British fort in western Pennsylvania in the years immediately before the American Revolution. It had previously been known as Fort Duquesne and Fort Pitt.
During the late 1740s, William Trent, an Englishman engaged in the fur trade with Ohio Country Indians, built a trading post at the headwaters of the Ohio River (modern-day Pittsburgh). Trent and the other English traders quickly prospered. They could easily trade with Ohio Country natives and others in northwestern Pennsylvania via the two rivers - the Allegheny and the Monongahela - that came together here to from the Ohio River. .