Although Charbonneau and Sacajawea were considered man and wife, they had never been officially married in the eyes of the Church. Charbonneau had another wife at the same time as Sacajawea named Otter Woman. Although he had purchased or won Sacajawea from the Hidatsa, she was not upset with her situation. Many young Indian girls of the Great Plains desired marriage to a trader or trapper, as such a wedding would mean an improved standard of life in many cases.

Considering the great amount of hardship in Sacajawea's life, she maintained an incredible stoicism and even cheerfulness: the woman was captured, sold, married to her purchaser (who already had another wife!), and taken on a dangerous and difficult expedition. Lewis called the ease with which she accepted tough situations "either philosophy or folly." Because it seems unlikely that Sacajawea knew of the overall significance of her help to Lewis and Clark--she probably never understood the expedition's meaning for the fledgling U.S.--her motivation throughout all the hardship apparently stemmed merely from a great personal devotion to her husband and the expedition's captains.

Lewis and Clark hired Charbonneau as an interpreter of Indian languages, although he communicated with Indians mostly by sign language. He was the oldest man on the expedition (46) and he caused lots of problems, including nearly capsizing a boat and losing two horses. Sacajawea proved more capable then her husband. Still, as a man in his late forties, it was impressive just that he survived the grueling expedition.

Translation proved very difficult. Often, Lewis and Clark would say something in English to a French-speaker, who would pass the message to Charbonneau, who would pass the message to Sacajawea, who would pass the message to a Shoshoni prisoner the tribe had, who would then announce the message to the chiefs. (And vice-versa, when the chiefs wished to say something to Lewis and Clark!)

Since the Lewis and Clark Expedition helped open the way for the exploitation of the American West by white settlers, some feel that in helping Lewis and Clark so greatly, Sacajawea was (inadvertently) betraying her people. From an entirely different angle, others criticize her decision to lead the expedition through Rocky Mountains via the Bozeman Pass, which some considered a poor choice because of its swampy line of approach.

The United States acquired the vast Louisiana Territory from Napoleon in 1803, when Napoleon, for whom the British could potentially block access to the New World, decided to free himself of his transatlantic commitments. When Thomas Jefferson authorized the purchase of the territory from France, no one really had much of an idea of the area's immense size. (In fact, the Louisiana Purchase doubled the geographic size of the United States, providing a frontier filled with fertile land that would take decades to populate with settlers.) The U.S. Government thus immediately dispatched explorers into the newly purchased region, and chose Meriwether Lewis and William Clark to lead an expedition (1804-1806). Their mission was to find a hypothesized water-route linking the Atlantic and Pacific oceans. Although they were unable to find such a route (none exists), Lewis and Clark catalogued the area they traversed, and in many cases became the first white men ever to set eyes on much of the natural wonder of the American West. And they did make it to the Pacific Ocean, though their path ended up having to include both water and land routes. Thus, the Lewis and Clark expedition took the first step in consolidating this new, vast region into the United States.

Clark had a very close relationship with Sacajawea, whom he nicknamed "Janey." He described her helpfulness in glowing terms in his journal, and wrote that he felt bad that the expedition did not have enough money to pay her. Clark later attempted to repay Sacajawea by raising and educating her son, Jean Baptiste. Because of his obvious fondness for Sacajawea, some writers have suggested the (unlikely) possibility that they had an affair during the Lewis and Clark Expedition.

Carrying her infant Jean Baptiste ("Pomp"), Sacajawea reassured suspicious and potentially hostile Indians that the Lewis and Clark expedition was not in their territory to make war. Her quickness saved the expedition's scientific equipment and journals from being lost in the Missouri River. She collected roots and berries along the way, helping to feed the mission and provide some diversity to the diet. She was extremely helpful in negotiating for horses with the Shoshoni, especially since her brother, Cameahwait, was the Shoshoni chief they encountered. She also helped identify when Native American groups were near (but not in sight) and let Lewis and Clark know what tribes they were near. Finally, she guided Clark's group (when the expedition was divided) through the Rocky Mountains via Bozeman's Pass.

There is debate over this issue. Most put her death in December of 1812, at Fort Manuel in South Dakota. This is based on Charbonneau presence there and the death of a Shoshoni woman who spoke French. The Shoshoni account says she left Charbonneau and came to live with her tribe until her death in 1884. Both theories have some evidence to back them up, and neither is watertight.