In 1864, Denver’s Colonel John Chivington led what is widely considered the most murderous campaign ever perpetrated against American Indians—the Sand Creek Massacre. It was not his first display of ruthlessness and violence. In fact, just a few short years earlier, Chivington had marched with 1,000 Union volunteers from Colorado to New Mexico to fight an invading army of Texas Confederates. The Coloradans’ long trek south is one of the most spectacular—and seldom-told—feats of the Civil War.