In 1803, the Louisiana Purchase transferred from France to the United States part of what is now Alberta and Saskatchewan. In 1818, the U.S. ceded the area to Britain. Most of what is now Saskatchewan was part of Rupert's Land and controlled by the Hudson's Bay Company, which claimed rights to all watersheds flowing into Hudson Bay, including the Saskatchewan River, Churchill, Assiniboine, Souris, and Qu'Appelle River systems.