Sacagawea was a Shoshone woman who served as an interpreter and guide for the Lewis and Clark Expedition from 1804 to 1806. She helped them communicate with other Native American tribes and navigate the territory from the Dakotas to the Pacific Ocean. The expedition's goal was to explore the Louisiana Purchase and establish trade and U.S. sovereignty over the Northwest. Sacagawea proved invaluable to the expedition's success and helped them achieve their mission of discovering a practical route across the western half of the continental United States.