Brower's Spring, Natural spring in Centennial Mountains, Montana.

Brower's Spring is a small flow of water emerging from the base of a cluster of dark grey, jagged rocks in the Centennial Mountains of Beaverhead County, Montana, at about 8,800 feet on the north fork of Hell Roaring Creek. The water collects into a tiny, shallow pool among irregular, blocky boulders coated with patches of green moss and low foliage. Small clusters of pink flowers grow on the lower right rocks, and a slender, weathered, pale trunk stands vertically on the right side of the channel.

Surveyor Jacob V. Brower visited the site in 1895 and in 1896 declared it the utmost source of the Missouri River in his book The Missouri River and Its Utmost Source. He buried a copper plate nearby engraved with the river's name and the date; the plate has never been found. The spring lies about 100 miles farther upstream than the source Meriwether Lewis reported in 1805 above Lemhi Pass.

The name comes from surveyor Jacob V. Brower, who visited in 1895 and buried an engraved copper plate nearby; the plate has never been found. A rock pile now marks the spot, and the spring is not an official name in the USGS Geographic Names Information System.

Access requires preparation for remote mountain conditions and difficult terrain, including crossing steep slopes below a ridge line. Visitors should bring weather-appropriate gear and navigation tools to safely travel in this isolated area.

The water flows through a complex system of multiple lakes and streams before merging into larger rivers that eventually reach a major waterway hundreds of kilometers away. This hidden source remains unknown to many despite being the origin of one of the continent's largest river systems.