William Clark took a real liking to the boy and called him "Little Pomp" probably taken from a Shoshoni word meaning "Leader". At the end of the Lewis and Clark adventure, Captain Clark made an offer to Sacagawea to help raise the boy in St. Louis and to give him an education. Sacagawea took him up on the offer and brought Jean Baptiste to St. Louis in 1809, when he was four years old. Clark adopted the young boy, raised him, and paid for his education.
Jean Baptiste had a few jobs in his lifetime, most were in the great outdoors, hunting, fishing and guiding. One of the few office jobs Jean Baptiste held was that of a public administrator and judge in California. He had a hard time in the position, because he didn't care for the way the local ranchers treated the Indians. This job lasted only a year and soon Jean Baptiste was off to find gold in Sacramento, a place he called home for 18 years.
The gold bug bit again when Jean Baptiste was 61, and he packed up and headed out to find his fortune in Montana. He never made it however. Jean Baptiste Charbonneau died along the trail at Danner, Oregon of pneumonia.
In July 1806, during the return trip home, Clark and his party traversed Bozeman Pass, set out down the Yellowstone River, and headed for the caches at Beaverhead. (caches meaning supplies they had placed on their way to the Pacific) Along the way, the crew came across a prominent rock formation, located on the south bank of the river in present-day Nibbe, Montana.
Naming the anomalous natural formation after young 'Pomp' Charbonneau, 
Clark wrote of the discovery in his journal that evening: At 4PM I arrived at the remarkable rock situated in an extensive bottom.This rock I ascended and from it's top had a most extensive view in every direction. This rock which I shall call Pompy's Tower is 200 feet high and 400 paces in secumpherance and only axcessible on one side which is from the N.E. the other parts of it being a perpendicular clift of lightish coloured gritty rock.The Indians have made 2 piles of stone on the top of this tower. The nativs have ingraved on the face of this rock the figures of animals &c
Clark, too, left his mark at Pompey's Pillar, engraving his name and the date into the stone; still visible, his mark is probably the only extant on-site evidence of the entire expedition.
Pompey's Pillar is now a National Monument and National Historical Landmark.