Picacho Pass runs between Picacho Peak and the Picacho Mountain Range and is the site of the only Civil War Battle fought in Arizona . The skirmish took place in April 15, 1862, when troops from the Union's California Volunteers came up to a detachment of soldiers on guard duty from the Confederate's Texas Volunteers.

Twelve Union cavalry troopers and one scout, commanded by Lieutenant Barrett, were conducting a sweep of the Picacho Pass area, looking for Confederates reported to be nearby. During their patrol they discovered and captured 3 Confederate lookouts, but failed to see 7 other Confederate soldiers before they opened fire. During the ensuing skirmish, Lt. Barrett and 2 of his men were killed and 3 others wounded. More than an hour later, both sides withdrew from the scene.

The remains of two Union soldiers buried at Picacho were later returned to California, but Lt. Barrett's grave, near the present railroad tracks, remains unmarked and undisturbed. Union reports indicate 2 Confederates may have been wounded, but there is no confirmation of this.