List of Colorado Territory Civil War units

On April 12, 1861, South Carolina artillery opened fire on Fort Sumter to start the American Civil War.

While many gold seekers in the Colorado Territory held sympathies for the Confederacy, the vast majority remained fiercely loyal to the Union cause.

An infantry, two cavalry regiments, and an artillery battery were sent to the support Union operations, while others were raised for internal defense.

On March 28, the Coloradans and local New Mexico volunteers stopped the Texans at the Battle of Glorieta Pass, destroyed their cannon and supply wagons, and ran off 500 of their horses and mules.

Having lost the supplies for their campaign and finding little support in New Mexico, the Texans abandoned Santa Fe and returned to San Antonio in defeat.