The northern Ontario river has its headwaters near the western border of the province.

[citation needed] Its drainage basin area is 102,800 km2 (39,700 sq mi),[1] a small portion of which is in Manitoba.

The mouth of the river was located by the English in 1631 during expeditions by captains Thomas James and Luke Foxe.

[3]: 13, 28  Later, Fort Severn was established there as a trading post in 1689 by the Hudson's Bay Company.

The post, rebuilt in 1759, has been in continuous operation to this day making this community one of the oldest European settlements in Ontario.