Mount Jefferson stands on the Continental Divide at the Idaho-Montana border and is the highest point in the Centennial Mountains. Its significance lies in its opposing drainage: water from its south and west sides flows through Hell Roaring Creek into the Missouri River system, ultimately reaching the Mississippi and the Gulf of Mexico, while water from its northeast slope drains by way of Duck Creek, Henrys Lake, the Henrys Fork, and the Snake into the Columbia River and the Pacific. On its east flank, Brower’s Spring is widely regarded as the absolute headwaters of the Missouri River. The mountain was named for Thomas Jefferson.