Powder River Expedition (1865)

This event should not be confused with the Big Horn Expedition during the Black Hills War.

The Powder River Expedition of 1865, also known as the Powder River War or Powder River Invasion, was a large and far-flung military operation of the United States Army against the Lakota Sioux, Cheyenne, and Arapaho Indians in Montana Territory and Dakota Territory. Although soldiers destroyed one Arapaho village and established Fort Connor to protect gold miners on the Bozeman Trail, the expedition is considered a failure because it failed to defeat or intimidate the Indians.

Background

The Sand Creek massacre of Cheyenne people on November 29, 1864 intensified Indian reprisals and raids in the Platte River valley. (See Battle of Julesburg) After the raids, several thousand Sioux, Cheyenne and Arapaho congregated in the Powder River country, remote from white settlements and confirmed as Indian territory in the 1851 Treaty of Fort Laramie.

The Indians perceived the Bozeman Trail, blazed in 1863 through the heart of their country, as a threat. Although roads through the Indian territory were permitted by the Fort Laramie Treaty, they harassed miners and other travelers along the trail. At the Battle of Platte Bridge in July 1865, over a thousand warriors attacked a bridge across the North Platte River and succeeded in temporarily shutting down travel on both the Bozeman and Oregon Trails. After the battle, the Indians broke up into small groups and dispersed for their summer buffalo hunt. A weakness of Indian warfare was that they lacked the resources to keep an army in the field for an extended period of time.