Why is sacagawea famous?

Sacagawea acted as guide and interpreter to explorers Meriwether Lewis and William Clark in their expedition to chart and study the Missouri River and the American Northwest in 1805-1806 (when the area was still inhabited almost exclusively by Amerindian tribes).

Sacagawea, a Shoshone woman, accompanied her French trapper husband Jean Baptiste Charbonneau. She acted as a guide and interpreter, and especially as a visible sign that the expedition was a peaceful one.