What Sacajawea identified this landmark that later became a name for one of Montana's first countries?

Sacajawea identified the landmark known as the "Three Forks" of the Missouri River during the Lewis and Clark Expedition. This area, where the Jefferson, Madison, and Gallatin rivers converge, played a significant role in the exploration of the West. It later became the name for Gallatin County, one of Montana's first counties, reflecting its historical importance in American exploration and settlement.