The Continental Divide runs along the crests of the Rocky Mountains from Canada to Mexico, literally dividing the waters of the North American continent. Montana is known as a headwaters state because much of the water that flows to the rest of the nation comes from the mountains of Montana. Within its borders are portions of two major river drainage systems of North America. The Kootenai, Clark Fork, Blackfoot, Bitterroot and Flathead Rivers join the Columbia River, which flows into the Pacific Ocean. From its headwaters at Three Forks, the Missouri River empties into the Mississippi flowing to the Gulf of Mexico.