On March 8, 1859, the United States Senate advised and consented to the Hellgate Treaty, signed nearly four years earlier at Hell Gate in the Bitterroot Valley. The agreement bound the Flathead, Kootenai, and Upper Pend d’Oreille peoples—constituted as the Flathead Nation—to cessions and a reservation framework negotiated by Isaac I. Stevens.

President James Buchanan proclaimed the treaty on April 18, 1859. Ratification turned a frontier council’s promises into federal law and reshaped land, hunting, and political life across western Montana.

The long delay between signing and Senate action left tribal communities waiting while settlers and railroads pressed west. The ratified text remains a foundational—and contested—document in Montana’s tribal and territorial history.