St. Vrain died along with three companions while on a mission to deliver dispatches from Dixon's Ferry to Fort Armstrong, both in Illinois.
[1] St. Vrain married Marie Pauline Grégoire in 1822, and eight years later settled in Kaskaskia, Illinois, a former French colonial city in the 18th century.
[1] Operating a sawmill in Kaskaskia, St. Vrain was 31 years old when he was appointed to replace Thomas Forsyth as a US Indian agent.
[1] He was assigned to the Sauk and Fox nations around Rock Island, Illinois during William Clark's tenure as superintendent of the St. Louis Indian Agency.
[2] St. Vrain had almost no experience dealing with Indians but, as a member of a politically important St. Louis-French family, he had connections to U.S.
The story circulated upon his death by Governor John Reynolds was that St. Vrain was keenly in tune with Indian culture and was treacherously murdered by a chief who had adopted him as a brother, even naming him Little Bear.