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. .
In the early 1750s, the French attempted to deny England access to the Ohio Country. In 1754, a French military force captured Trent's outpost and began to construct Fort Duquesne. The French also captured several other English settlements in western Pennsylvania. France's seizure of land that the English and their colonists claimed would eventually lead to the French and Indian War (1756-1763). Between 1754 and 1758, the British struggled to recapture their former possessions. Finally, in 1758, they were victorious.
After securing Fort Duquesne, the English renamed it Fort Pitt in honor of William Pitt. Pitt, the English Prime Minister during the French and Indian War, had determined that the only way that England could defeat France in Europe in this war was first to conquer the French in the New World. He sent thousands of British soldiers to North America to assist the English colonists in driving the French from the continent. By 1759, the English had secured practically all of France's possessions in North America. The New World portion of the war came to a close. Under the Treaty of Paris (1763) France relinquished control of all of its former territories in North America to England.
Fort Pitt remained under England's control until the American Revolution, when the colonists gained possession of it. The fort served as an important trading post with the Ohio Country natives for both the English and the Americans. As more and more Americans sought to improve their fortunes by moving into the Ohio Country, Indians began to attack the settlers. The fort's garrison actively protected whites moving into the region. In the mid-1770s, the English renamed the installation Fort Dunmore. John Murray, Lord Dunmore, served as the royal governor of New York and later in Virginia. Once the colonists declared their independence, they renamed the fortification Fort Pitt.