Who is Toussaint Charbonneau from The Journals of Lewis and Clark and what is their importance?

Toussaint Charbonneau was a 45-year-old independent fur trader from Canada when he first visited Fort Mandan on November 4, 1804. He could speak fluent French and Hidatsa, but no English. He told the captains he wished to be hired as an interpreter. In March of the following year, Charbonneau was officially enlisted with the Corps as an "interpreter through his wife," along with the latter. Sacagawea was sixteen years old at the time, and the mother of a newborn son, Jean-Baptiste Charbonneau. This establishes a rather strange chain of communication, where Sacagawea speaks Shoshone to the natives, then translates it to Hidatsa for her husband; Charbonneau then translates from Hidatsa to French, and Labiche does the same from French to English for the Captains.

Upon their return to Fort Mandan on August 14, 1806, Charbonneau was paid $500.33 for his services and discharged. William Clark eventually adopted both of Charbonneau's children, one of which is Baptiste. Toussaint Charbonneau disappeared at the age of 80.