Decision Point - Confluence of the Missouri and Marias rivers, MT. On June 3, 1805, the main party stayed at the fork of the river for several days while Lewis took a crew north and Clark took another south. When they returned, still uncertain which fork was the Missouri, the captains decided to proceed up the south fork. Upon hearing the falls, Lewis knew he was on the Missouri. He named the north fork the Marias after his cousin.
