The English colonies in North America continued to grow. By 1750, colonial governors began to cast covetous eyes on the Native lands to the west. In New France, Governor La Jonquière took steps to thwart any Anglo-American attempt to move across the Appalachian Mountains into the Ohio River area.
In 1749, Céloron de Blainville travelled through the Ohio region to formally claim the lands for the King of France. A large force of Canadian militia accompanied him. De Blainville also established and reaffirmed alliances with the First Nations of the Ohio. The following year, the French began to construct a line of forts along the route to the Ohio Valley. In 1750, they established Fort Rouillé (Toronto) on the north shore of Lake Ontario. French troops constructed the fortified settlement of Presq'isle on the south shore of Lake Erie in 1751. The next year, the Canadian militia built two more forts south of Presq'isle, Fort le Boeuf and Fort Venango. In 1753, Pierre Marin, Sieur de la Malgue, led an expedition of 2,000 Troupes de la Marine, Canadian militia, and Native allies into the Ohio Valley. They surprised a group of Virginians constructing a fort where the Allegheny Rivers flows into the Ohio (site of present-day Pittsburgh). Marin quickly forced the Virginians to leave, and his men completed the fort. He named it Fort Duquesne, in honour of the new governor of New France.