In exchange for safe passage for emigrants along the Oregon Trail, which ran south of their core territory, the Lakota and other nations received annuity payments in goods.

Whatever the limitations of that 1851 agreement — and there were many, including questions about whether the full range of Lakota people recognized its validity — it represented a formal U.S. acknowledgment that the Powder River Country was not available for American settlement or development.

That acknowledgment would not last long.

Gold Changes Everything

The pressure that ultimately forced the confrontation over the Bozeman Trail came from a familiar direction: the discovery of gold.

Gold had been found in the mountains of Colorado and the Sierra Nevada in the preceding decades.