From Ohio History Central
Fort Pitt was a British and American fort in western Pennsylvania in the years after the French and Indian War (1756-1763). It had previously been called Fort Duquesne and was also briefly known as Fort Dunmore.
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 form the Ohio River. .