
In his journals, Captain William. Clark described the Yellowstone River, which he translated from the French name,
Roche Jaune, as
"...120 yds. Wide bold, rapid and deep." Clark and his party followed the Yellowstone River for 19 days to its confluence with the Missouri River (just across the border of present day North Dakota) where they planned to meet the rest of the Corps on August 3, 1806.
Native Americans referred to this feature of the river where you now are as "the Big Bend," because the river abruptly changes from its northward course to flow east. The Crow, or Apsaalooke, called it the Elk River or "Lichiilikaashaashe."
The Yellowstone River is the longest free-flowing river in the United States. It is over 670 miles long, from the southeast of Yellowstone National Park in Wyoming to the Missouri River in North Dakota.

William Clark's map and journal. Clark's maps were drawn so accurately that they were used by fur trappers, prospectors, and early pioneers.
Erected by Lewis and Clark National Historic Trail, National Park Service.