Benjamin O'Fallom was born on Semptember 20, 1793, in Kentucky, the son of Dr. James O'Fallon and Frances Eleanor Clark, the youngest sister of William and George Rogers Clark. Dr. O'Fallon died soon after Benjamin was born and the infant came under the guardianship of his uncle William Clark, who resided at St. Louis.
Benjamin O'Fallon was reared and attended a school in St. Louis.
In 1816, Benjamin O'Fallon wrote from St. Louis to his brother John that he had sold his mill establishment and was about to set out to trade with the Sioux because his pride would not permit him to do business on so small a scale as he had done in St. Louis. He became Indian agent at Prairie du Chien and in 1817 made treaties between the United States and the Otos and Poncas. In 1819 he was appointed Indian agent for the Upper Missouri, acquiring the title of major. Under his jurisdiction were the Pawnees, Otos, Missouris, and Omahas. With his deputy and interpreter, John Dougherty, he joined the Yellowstone Expedition led by Major Stephen H. Long at St. Charles and accompanied it to Council Bluffs, where he made his headquarters.
The expedition was designed for the several purposes of protecting the growing fur trade, controlling the Indian tribes, and lessening the influence which the British trading companies were believed to exert upon them, but it failed to get sufficient appropriation from Congress to complete its work. The copies of Major O'Fallon's speeches at the councils with the Indians at Engineers Cantonment quoted by Major Long show that he was an orator of no mean ability and that he possessed a remarkable knowledge of Indian customs, habits, and characteristics.
During the winter of 1821 O'Fallon acted as a guide for a group of Pawnees who visited the chief cities of the Eastern states, performing for the curious. On his return to Council Bluffs he resumed his duties as "Father" to the tribes. In 1825 he signed fifteen treaties between the United States and Indian tribes in the Upper Missouri country. He resigned his position as agent in 1827 and returned to St. Louis. The following year he was named presidential elector for General Jackson from Missouri. He retired to Jefferson County, where he died fourteen years later.
Serving as an Indian agent for the Upper Missouri since 1819, Benjamin O'Fallon contributed a lot to the development of relations between Americans and Indians. In 1825 he signed fifteen treaties between the United States and Indian tribes in the Upper Missouri country. O'Fallon's memory is perpetuated in the West by O'Fallon's Creek in Montana, which was named in his honor by Gov. William Clark on the Lewis and Clark Expedition, while Benjamin was yet a boy.
Honest and courageous, his bravery reaching the point of foolhardiness, O'Fallon was efficient in the discharge of his duties, though he occasionally lost control of his temper.
While at St. Charles, in November 1823, Benjamin O'Fallon married Sophia Lee, who bore him six children.
