For many generations, Native peoples came from all directions to the confluence of the Missouri and Yellowstone rivers for abundant bison and other game, maintaining seasonal settlements so they could follow migrating herds, and the area became important for both intertribal trade and hostilities. During their winter at Fort Mandan, Lewis and Clark heard much from native hunters about the Yellowstone River and its meeting with the Missouri River, and on April 25, 1805, Meriwether Lewis praised the wide and fertile valleys of the two rivers and the country’s many herds of buffalo, elk, antelope, and deer. At a place commended by Clark, the American Fur Company later built Fort Union Trading Post to serve the Assiniboine and other Northern Plains tribes, and for much of its history from 1828 to 1867 it was the westernmost port for shipping furs by steamboat to the East. When Prince Maximilian arrived at Fort Union Trading Post on June 24, 1833, he found a gathering of about one hundred people from many nations, including Americans, Englishmen, Frenchmen, Germans, Russians, Spaniards, and Italians. Both rivers remain important for carrying snowmelt from the Rocky Mountains into the arid Great Plains; today the Army Corp of Engineers manages the flow of the Missouri River from six major reservoirs for downstream water needs, while the Yellowstone remains the largest free-flowing river in the country.