The French and Indian War covered a large area of the American colonies. The St. Lawrence River which drained from the Great Lakes and ran past Quebec was not only the border between French Canada and the British colonies to the south. It was also a major French route of trade and transportation. Connected to it were three river systems that played an important part in the conflict between Britain and France.
Traveling from Presque Isle on Lake Erie the French could make a short portage and get into a tributary of the Allegheny River. At the "Forks of the Ohio" the Allegheny River joined the Monongahela River to form the Ohio River. The Ohio River eventually joined the Mississippi. The French could use this route to travel by boat from Quebec to New Orleans. In 1753 the French began to construct a chain of forts to protect this important transportation route. In the spring of 1754 the French began building Fort duQuesne at the Forks of the Ohio. This initiative was one of the events that spurred the British to take action against the French and start the French and Indian War. Virginia Governor Dinwiddie in Williamsburg sent George Washington to destroy Fort duQuesne. This campaign ended with Col. Washington's defeat (his only surrender during his military career) at Fort Necessity and his return to Ft. Cumberland.
Another early transportation route discovered by the French was the Champlain corridor which traveled south from the St. Lawrence River on the Richelieu River into Lake Champlain and Lake George and then portaged to the Hudson River that ran south to New York. Among the first forts constructed by the French on territority threatening Britian was Fort St. Frederick; at the end of the war it became the British Fort Crown Point. South of it was Fort Carillon later to become famous as Ft. Ticonderoga. At the south end of Lake George was the British Ft. William Henry, later made famous by the book, Last of the Mohicans.
An off-shoot of the Champlain route was the route from Albany, New York to the French Ft. Oswego on Lake Ontario. This route (and Forts Niagara and Oswego) would figure in several campaigns of the war.