<P> Fort Duquesne , located at the confluence of the Allegheny and Monongahela Rivers at the site of present - day Pittsburgh , Pennsylvania , guarded the most important strategic location in the west at the time of the Seven Years ' War . It was built to insure that the Ohio River valley remained under French control . A small colonial force from Virginia began a fort here but a French force under Claude - Pierre Pécaudy de Contrecœur drove them off in April 1754 . New France claimed this as part of their colony and the French were anxious to keep the British from encroaching on it . The French built Fort Duquesne here to serve as a military stronghold and as a base for developing trade and strengthening military alliances with the Aboriginal peoples of the area . </P>
how did france try to protect its land claims in the ohio river valley
built Fort Duquesne