river in southern Alberta, Canada, the main headstream of the South Saskatchewan River. It rises in the Canadian Rockies of Banff National Park at the foot of Mount Gordon and flows from the glacial Bow Lake southeastward for 365 miles (587 km). It joins the Oldman River 37 miles (60 km) west of Medicine Hat and thus forms the South Saskatchewan River. The river was so named because the Cree Indians made bows from Douglas firs that grew along its banks. French explorers traversed the Bow valley in 1752, followed by fur traders in the early part of the 19th century. Several dams have been built on the Bow and its tributaries; they are used for hydroelectric power, irrigation, and flood control, as well as for providing Calgary—the largest settlement on the river—with its water supply. Bow Valley Provincial Park lies at the junction of the Bow and Kananaskis rivers, 50 miles (80 km) west of Calgary.