Canada has five ocean drainage basins. The largest by far is the Hudson Bay basin; the smallest, situated in the southern Prairies, flows via the Missouri and Mississippi rivers into the Gulf of Mexico. Within each basin lie smaller subbasins. Drainage divides separate the basins. The best known of these is the Continental Divide of the Rockies, which separates rivers flowing westward to the Pacific from rivers flowing to the Arctic and Hudson Bay.
A map of Canada opens automatically, and colour keys show drainage basins across the country.