Portage la Prairie is located approximately 75 kilometres (47 mi) west of Winnipeg, along the Trans-Canada Highway (located exactly between the provincial boundaries of Saskatchewan and Ontario), and sits on the Assiniboine River, which flooded the town persistently until a diversion channel north to Lake Manitoba (the Portage Diversion) was built to divert the flood waters. The city is surrounded by the Rural Municipality of Portage la Prairie.