On August 5, 1833, four days before its arrival at Fort McKenzie, the westernmost point of the expedition, the expedition’s keelboat stopped on the opposite side from an encampment of some two hundred Atsina or Gros Ventres tipis located at the mouth of the Judith River.

The travelers were approached by a large number of villagers who wanted to trade or receive gifts. The Atsina far outnumbered the boat's passengers and crew, who considered the situation dangerous. Bodmer quickly recorded the scene (on view next to this print) before getting away. Fortunately, he was able to portray two chiefs, Niatosha and Mexkemauastan, who boarded the keelboat at this time. Mexkemauastan, or "Stirring Iron," who had threatened to kill the superintendent at Fort McKenzie the year before, seemed friendly enough when he met Maximilian’s party. Bodmer's portrait depicts him as a somewhat morose, intimidating figure. His hairstyle, featuring a large knot on top of his head, indicates his special status as a medicine man in his tribe.