arrived during the siege, but the fort held out. The fighters eventually began to disperse, forcing Procter and Tecumseh to return to Canada. Along the way they attempted to storm Fort Stephenson, a small American post on the Sandusky River near Lake Erie. They were repulsed with serious losses, marking the end of the Ohio campaign. Captain Oliver Hazard Perry fought the Battle of Lake Erie on 10 September 1813. His decisive victory at Put-in-Bay ensured American military control of the lake, improved American morale after a series of defeats and compelled the British to fall back from Detroit. This enabled General Harrison to launch another invasion of Upper Canada, which culminated in the American victory at the Battle of the Thames on 5 October 1813, where Tecumseh was killed. American West, 1813–1815 The Mississippi River valley was the western frontier of the United States in 1812. The territory acquired in the Louisiana Purchase of 1803 contained almost no American settlements west of the Mississippi except around St. Louis and a few forts and trading posts in the Boonslick. Fort Belle Fontaine was an old trading post converted to an Army post in 1804 and this served as regional headquarters. Fort Osage, built in 1808 along the Missouri River, was the westernmost American outpost, but it was abandoned at the start of the war. Fort Madison was built along the Mississippi in Iowa in 1808 and had been repeatedly attacked by British-allied Sauk since its construction. The United States Army abandoned Fort Madison in September 1813 after the indigenous fighters attacked it and besieged it—with support from the British. This was one of the few battles fought west of the Mississippi. Black Hawk played a leadership role. The American victory on Lake Erie and the recapture of Detroit isolated the British on Lake Huron. In the winter a Canadian party under Lieutenant Colonel Robert McDouall established a new supply line from York to Nottawasaga Bay on Georgian Bay. He arrived at Fort Mackinac on 18 May with supplies and more than 400 militia and Indians, then sent an expedition which successfully besieged and recaptured the key trading post of Prairie du Chien, on the Upper Mississippi. The Americans dispatched a substantial expedition to relieve the fort, but Sauk, Fox, and Kickapoo warriors under Black Hawk ambushed it and forced it to withdraw with heavy losses in the Battle of Rock