At the outlet of the Niagara River into Lake Ontario, this promontory was a strategic point for controlling the route to the interior Great Lakes region. The French recognized its importance early, and LaSalle in 1678 and Denonville in 1687 erected temporary fortifications. In 1726 DeLery built Fort Niagara for the fur trade, an imposing structure with massive stone walls that resembled a French chateau and was called "The Castle." As rivalry with France for control of North America intensified, the fortification irritated the British. Captain Pouchot, a French engineer, strengthened the fort in anticipation of a British attack, but British troops, with colonials and Indians, assaulted it, and after an 18-day siege Sir William Johnson forced the French to surrender on July 25, 1759. The British improved Fort Niagara, used it for fur trading, and during the American Revolution made it their base for raiding the New York frontier. They did not relinquish it until 1796. Following an American invasion of Canada in the War of 1812, British forces again captured Fort Niagara on December 19, 1813. The peace treaty of 1814 returned the fort to the United States. Old Fort Niagara stands today as a memorial to soldiers who served here under three flags.