Saleesh House, also known as Flathead Post, was a North West Company fur trading post built near present-day Thompson Falls, Montana in 1809 by David Thompson and James McMillan of the North West Company. It became a Hudson's Bay Company (HBC) post after that company merged with the North West Company in 1821. Under HBC control the post was better known as Flathead rather than Saleesh. It continued to operate until at least 1855.
Thompson had established the post of Kullyspell House earlier in the year in the territory of the Pend d'Oreilles (who Thompson called the Kullyspel, an early variant spelling of "Kalispell"). This post was sited near the mouth of the Clark Fork river. By October Thompson had decided to established another post farther up the Clark Fork in the territory of the Flatheads. Thompson's name for the Flatheads was Saleesh. He also called Clark Fork the Saleesh River. The Saleesh House trading post was built by the end of 1809.
Joint British - U.S. occupation of areas west of the Rocky Mountains continental divide pursuant to the Treaty of 1818 ended with the Oregon Treaty in June, 1846, which extended the international boundary along the 49th parallel from the ridge of the Rocky Mountains to the Pacific Ocean.