According the the Family Tree Book of Antoine LeBeau, Sr. prepared by Casimir L. LeBeau: Antoine Sr. was born in France about 1830. He came to Quebec, Canada, and from there came down to St. Louis, Missouri. From St. Louis he worked his way up the Missouri River. He married Mary Little Thunder, by Indian Custom, about 1847. They had five sons. He worked for the American Fur Co. They lived about 5 years at old Fairbanks, on the East side of the river 1/2 way between old Ft. Pierre and the old Cheyenne Agency. Around 1872 they moved up by Swan Creek and started a trading post, The area around his storn grew into a town called LeBeau. Around 1884 they moved back to the west side of the river and began ranching (cattle and horses). Hope this helps.