In the late 1850s and early 1860s Arizona was desperately lobbying to become a territory separate from New Mexico. It did everything in its power but was hindered by national politics it could not control. When the Civil War broke out in 1861, Arizona allied itself with the South and allowed the Confederacy to take control of the territory. Colonel John R. Baylor of the Confederate States of America defeated Union troops in Arizona and New Mexico in March 1861. Baylor was later named governor in January 1862. He set up a territorial government for the Confederacy with its own constitution. On February 14, 1862, Arizona officially became a Confederate Territory when it was annexed by President Jefferson Davis.

One of the most important defections was that of the commander at Fort Union, N.M., Major Henry H. Sibley, who returned to New Mexico as a Confederate general. Sibley arrived in San Antonio in August, where he organized three regiments of the Texas Volunteer Cavalry. Tucson was looming ever more important. Sibley, in 1862, detached a company of mounted rifles under Captain Sherod Hunter to take possession of friendly Tucson for the Confederacy. On March 3, Hunter led his command to the Pima Indian villages on the Gila River. He arrested Ammi M. White, a miller who has been buying grain and supplies for the Union troops. He learned that every station of the Butterfield Overland Mail had been provided with hay for Carletons soldiers; he burned six of these stations.

Meanwhile, Colonel James H. Carletons California Volunteers, or California Column, of at least 2,000 men, was concentrating on the invasion of Arizona. Carleton sent Captain William McCleave with the 1st California Dragoons to recon the Confederate forces. He ordered him to stop at the Pima villages and construct a new building to store wheat and flour from Ammi White's mill and to reconnoiter Tucson and retake the town. McCleave and his scouts fell into a trap. McCleave knocked at White's door and was greeted by Hunter posing as White, until the Confederates captured the Federals. Lieutenant Jack Swilling then escorted McCleave and White to Tucson. When the California Column at Fort Yuma learned of McCleave's capture, Carleton dispatched Captain William P. Galloway, with a Union vanguard of 272 men and a battery of two 12-pounder howitzers, to establish a base at the Pima villages and to head to Tucson to recapture McCleave. Galloway dispatched Lieutenant James Barrett to circle the Rebels from the east with about a dozen cavalrymen.

On April 15, 1862, Barrett's detachment approached Picacho Pass about 45 miles northwest of Tucson, and discovered three Confederate pickets at their base camp. Barrett charged the three dismounted Confederates. Shots were fired, and the gunfire alerted the other seven Confederate pickets who took a dismounted defensive position in the heavy chaparral. Barrett led his men single file through the thicket. It was a critical mistake. Confederate fire emptied four saddles; the Federals regrouped; and the Confederates retired into the thicket and reloaded. Barrett followed them in and was shot in the neck and killed instantly. After 90 minutes of desperate fighting, the Union troops broke off the engagement. They took their wounded and the three captured prisoners with them. The Confederates removed their own wounded, Privates Daniel Gilleland and James Green, and rode to Tucson to warn Hunter. It became obvious that no support was coming for Hunter, and before long Carleton and the California Column would be occupying Tucson. Hunter knew Carleton had overwhelming forces and decided to remove his troops to Texas.

Arizona became a territory under the Union flag February 26 1863.

Picacho Pass (April 15, 1862), was thought to be the westernmost battle of the Civil War, but there was a skirmish at Stanwix Station, and farther west, the confrontation at La Paz on the Colorado River occurred. Blood was shed there in May 1863, when Union soldiers from Fort Yuma under the command of Lieutenant James Hale were ambushed in front of Michael Goldwaters store. A Confederate soldier killed two Union soldiers and wounded one.

The Arizona territory produced 1 Union Battalion for service in the Civil War. The Compiled Service Records contains 665 names.

1st Battalion, Arizona Infantry

Three units are identified for the Confederacy, but two of the units only have a few names on the roster.

Arizona Brigade - 2 names

Arizona Battalion - 1 name

Herbert's Battalion, Arizona Cavalry - 268 names

REF: http://www.azdema.gov/museum/famousbattles/pdf/CIVIL%20WAR%20IN%20ARIZONA-072109.pdf

http://history.sandiego.edu/gen/st/~paulb/uscivilwar/