The Lewis and Clark Expedition camped at the confluence of the Marias and Missouri rivers on June 2-12, 1805, and during the long stay the group rested while confronting a dilemma over which river flowed over the "Great Falls" described by the Mandan Indians. Information from the Mandans had been reliable to that point, but the discovery of the Marias River was unexpected. The right choice would lead to the best route across the Rocky Mountains, while a wrong one could leave the expedition stranded and unprepared for a potentially deadly winter. Lewis led a small party up the Marias and Clark another up the Missouri. The Missouri was clear with a rocky bed, traits of rivers that have recently emerged from the mountains, while the Marias was swollen and muddy from spring runoff. They chose the Missouri, and the captains' judgment was rewarded the next day when the falls were discovered.