On June 3, 1805 the expedition came to a fork in the river. They remembered that the Mandan had told him to take the fork of the river leading to the Great Falls. Lewis went ahead scouting. He reached the Great Falls on June 13. In fact they turned out to be five separate waterfalls over a 12mi (19 km) stretch of river.
Lewis got back to the rest of the expedition and the party began to carry their canoes and luggage around the five waterfalls. It took them more than a month just to get across this 12mi (20km) stretch.
