While in St. Louis, Bodmer painted the portraits of Sauk (Sac) and Fox delegation members who sought the release of Sauk leader Black Hawk. The war chief had been captured after several battles with the US Army on the Illinois frontier the previous year. William Clark invited Maximilian to meet the prominent prisoner and the Indian delegation members at Jefferson Barracks.

The prince negotiated with Kenneth McKenzie, superintendent of the American Fur Company's Upper Missouri outfit, to travel with him on the Yellow-Stone, a company steamboat that usually did not transport passengers. The explorers also consulted with McKenzie on necessary preparations for the voyage. In St. Louis, Bodmer and Maximilian also visited Swiss painter Peter Rindisbacher—known for his portraits of Canadian Indians—and they viewed paintings by George Catlin at the home of Major O'Fallon, who had accompanied major Long's expedition in the Great Plains area. On April 10, 1833, the travelers departed on the Yellow-Stone toward trading posts on the upper Missouri.