Battle of Julesburg
1865 CE.
Shown on the map at 40.939°, -102.378°.
The Battle of Julesburg took place on January 7, 1865, near Julesburg, Colorado between 1,000 Cheyenne, Arapaho, and Lakota Indians and about 60 soldiers of the U.S. army and 40 to 50 civilians. The Indians defeated the soldiers and over the next few weeks plundered ranches and stagecoach stations up and down the South Platte River valley.
Text from the Wikipedia article Battle of Julesburg, licensed CC BY-SA 4.0.