By the late 18th century, more than 1,000 Oto lived in earth-lodge villages along the Platte River. They were a southern Sioux band, related to the Iowa and Missouri tribes. Then epidemics decimated their tribes and the Oto and Missouri formed one band of about 250 people.
Lewis and Clark's expedition first encountered the Oto settlements in summer 1804, when the Oto were away buffalo hunting and their villages were empty. The Oto were farmer-hunters, growing and harvesting corn, beans, and squash, but also hunting bison and other game to supplement their diet. At one point, Clark lamented that the Corps might pass through the region before the Oto returned.
Based on information from a Missouri Indian, Lewis and Clark sent a party out to the joined Oto-Missouri village, and they returned with a small group on August 2.
The next day, at modern-day Council Bluffs, Iowa, Lewis and Clark held their first meeting with western Indians, setting the pattern for future such councils. Amid great pomp and ceremony the Corps marched in their full uniform regalia, demonstrating their weaponry and distributing gifts to those chiefs they felt were of sufficient rank.
Many times Lewis and Clark were oblivious to the rank and stature of individual chiefs, choosing one man they felt ranked above all others. This decision often caused rancor among the Indians and didn't aid the peace discussions.
Despite the success of these first meetings, Lewis still wanted to meet with the head Oto chief, Little Thief. A search party went out and on August 18 the Corps finally met with Little Thief and Missouri Chief Big Horse.
The discussions centered on trade and peace negotiations. Lewis wanted the Oto-Missouri to support peace on the Plains and to stop raiding the neighboring Omaha tribe. The Oto were more interested in a reliable, open-trade system.
Disappointed in the seemingly paltry gifts of beads, paint, and tobacco from the huge supply on the keelboat, both the Oto and the Missouri were unhappy with the exchange. This first Indian council ended on a flat note and nothing was really accomplished.
In March 1805, however, Little Thief joined a delegation of Oto, Missouri, and other local tribes to meet President Jefferson in Washington, D.C.
By the mid-1860s there were about 400 Oto-Missouri remaining, and they settled on a reservation on the Big Blue River between Kansas and Nebraska. In 1881 this combined tribe moved to Indian Territory in modern Oklahoma. The 1991 census listed about 1,350 Oto-Missouri still living near Pawnee, Oklahoma.