Marias River and Lewis and Clark

June 02, 2004


Referred by: Rod Benson, Helena High School Science Dept.
Summary authors & editors: Rod Benson

This aerial photo, shows the confluence of the Marias and Missouri Rivers in central Montana. When the Lewis and Clark expedition reached this confluence on June 2, 1805 they faced a tough decision. The Mandan tribe, which they had spent the winter with in North Dakota, made no mention of this "fork" in the river, so the expedition was not sure which way to go. As one historian put it, they had reached the "where the hell are we" phase of their expedition. In the photo it seems obvious which branch is the main channel (the Missouri River). Although they found the south fork to be wider compared to the north fork, the muddy water in the north fork more closely resembled the river that they had been traveling on since leaving the Mandan village earlier that spring. On the basis of its muddy appearance, the men strongly believed the north fork to be the route that they should take.

Lewis and Clark didn’t agree their men, but they realized the importance of choosing the right course. Clark, and a few of his men, went forty-five miles up the south fork, finding that it ran swift and true to the west of south. He returned convinced that it was the Missouri. Lewis and a small crew went nearly eighty miles up the north fork, confirming that it headed from too much to the north for their route to the Pacific. Their decision to follow the south fork was confirmed when they reached the great waterfalls that the Mandans had told them about (near present-day Great Falls, Montana).

Once Lewis determined that the north fork was not the Missouri he decided to name it Maria’s River in honor of his cousin, Miss Maria Wood. Over the years the apostrophe was dropped and the pronunciation changed to “ma-RI-us.” Permission to use the photo was obtained from Ron Lowery, author of "Chasing Lewis and Clark."

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