Portage la Prairie (pôrˌtĭj lə prârˈē) [key], city (1991 pop. 13,186), S Man., Canada. It is the center of a mixed-farming region and has diversified industries. The city is near the site of Fort La Reine, an important fur-trading post built (1738) by Vérendrye as a carrying point between the Assiniboine River and Lake Manitoba. The nearby Portage Diversion redirects Assiniboine floodwaters to the lake via a spillway.