The Missouri River of the U.S. rises along the Continental Divide in Montana and flows eastward across the Great Plains, receiving numerous tributaries along the way. It eventually empties into the Mississippi, north of St. Louis, which drains southward to the Gulf of Mexico. During the early European exploration of North America, the Missouri was an important route for traders and trappers; of course, it also provided navigation for the Lewis & Clark Expedition.
Farther north, in Canada, the Saskatchewan River mirrors the drainage of the Missouri. Its North Fork rises in the Rockies southwest of Edmonton while its South Fork heads as the Bow River, west of Calgary. After flowing through those respective cities, the primary forks cross the Central Plains of Canada and merge northeast of Saskatoon. From there, the combined Saskatchewan River continues eastward until it enters remnants of Lake Agassiz (Cedar Lake and thence Lake Winnipeg). The Nelson River drains Lake Winnipeg, flowing north and then northeast before entering Hudson Bay.
Like the Missouri, the Saskatchewan River, after dropping from the Rockies, once drained a vast prairie ecosystem, now converted to crop fields, ranchlands, towns and cities. And, like the Missouri, it played a vital role in the exploration and settlement of North America.
