He left New Orleans in 1816 after having been raised for a time by an aunt, and began working in the lower-Missouri fur trade in 1819.
He married Bright Sun, also known as Me-um-bane, a daughter of the Omaha Chief Big Elk.
Early in his career Fontenelle was involved in fur trading into the Rocky Mountains.
[1][2] However starting in the late 1820s he was in command at Fontenelle's Post in what would become Bellevue, Nebraska, along the Missouri River.
In 1831 he led a trading expedition to the Cache Valley of Utah and Idaho with Andrew Drips.