Why did President Thomas Jefferson send Lewis and Clark on an expedition? What did Lewis and Clark find on their journey west?

What was the name of the American Indian that traveled with Lewis and Clark? Why was he/she important?

1. President Thomas Jefferson commissioned the expedition shortly after the Louisiana Purchase in 1803 to explore and to map the newly acquired territory, to find a practical route across the western half of the continent, and to establish an American presence in this territory before Britain and other European powers

2. By the end of October the Expedition had made its way around the falls of the Columbia and sighted Mount Hood. In November the Pacific Ocean was sighted. Clark estimated in his journal that the party had traveled 4,162 miles from the mouth of the Missouri River

3. Sacagawea is best known for her association with the Lewis and Clark Expedition (1804–06). A Shoshone woman, she accompanied the expedition as an interpreter and traveled with them for thousands of miles from St Louis, Missouri, to the Pacific Northwest.

Explanation:

where is the picture?