Fort Pitt was a fort built by British forces between 1759 and 1761 during the French and Indian War at the confluence of the Monongahela and Allegheny rivers, where the Ohio River is formed in western Pennsylvania. It was near the site of Fort Duquesne, a French colonial fort built in 1754 as tensions increased between Great Britain and France in both Euro…Fort Pitt was a fort built by British forces between 1759 and 1761 during the French and Indian War at the confluence of the Monongahela and Allegheny rivers, where the Ohio River is formed in western Pennsylvania. It was near the site of Fort Duquesne, a French colonial fort built in 1754 as tensions increased between Great Britain and France in both Europe and North America. The French destroyed Fort Duquesne in 1758 when they retreated under British attack.