Assiniboine River (uh-SIN-uh-boin), 590 mi/950 km long, Canada; rising in S Sask.; flowing SE into Man. then E to the Red R. at Winnipeg. Named for the local Native Americans, the Assiniboine. The Qu’Appelle and Souris rivers are its chief tributaries. The Assiniboine valley is one of Canada’s leading wheat-growing areas. The river was explored by the Vérendrye family in 1736, and forts were built at its mouth and near the site of Portage la Prairie. Settlement spread W along the river from the Red R. valley to the plains.
