In the passage from "crossing the great divide," who is reunited at the rivers edge?

The expedition members and Lewis and Clark reunited at the river's edge in Crossing the Great Divide. The Corps split into two teams so Lewis could explore the Marias River. Lewis and Clark stayed separated until they reached the Yellowstone and Missouri Rivers on August 11, along with Clark's. Once reunited, the Corps was able to return home quickly via the Missouri River. They reached St. Louis on September 23, 1806.