Most of the 1st California was recruited from August to October 1861, with the exception of Company K, which was organized the following February. Many of its companies were formed from companies of the California Militia taken intact into federal service others from individuals drawn from the militia. James H. Carleton served as colonelJoseph R. West as lieutenant colonel and Edwin A. Rigg as major. It came under the command of the Department of the Pacific (later it would come under the Department of New Mexico).
After some training at Camp Downy[1] near Oakland and Camp Latham near Los Angeles. Companies D, F and G were sent to establish and garrison Camp Wright, in November 1861. Detachments from the camp captured Daniel Showalter‘s party near Warner’s Ranch, November 20–29, 1861. In December, 1861, five companies of the regiment were sent to Fort Yuma on the Colorado River and the others to various posts around Southern California.[2]
The regiment was assigned to a force called the California Column, which was commanded by Carleton and composed of one infantry regiment (the 5th) and parts of two cavalry regiments (the 1st and 2nd) of California volunteers and a company of Regular artillery. The Column was formed to drive the Confederate Army of New Mexico out of the eastern part of the New Mexico Territory. Due to supply problems, the force did not move out until February 1862. The 1st Infantry saw fighting at the Battle of Picacho Pass (only Company I) and the Battle of Apache Pass (this battle was against Apache warriors, not Confederates). The regiment continued marching across the New Mexico Territory to Fort Craig. Picacho Pass was the only engagement against Confederate forces, since they had retreated back into Texas before the California Column reached eastern New Mexico and they made no attempt to recover the territory they lost.
For the remainder of the war, the 1st California Infantry was engaged in garrison duty dispersed in posts across New Mexico Territory and Texas and fighting Apache and Navajo Indians in these places and in the Utah Territory. The unit was mustered out on October 21, 1866.

1st Regiment Cavalry2nd Regiment Infantry3rd Regiment Infantry4th Regiment Infantry5th Regiment Infantry6th Regiment Infantry
1st Regiment Infantry2nd Regiment Cavalry7th Regiment Infantry
1st Battalion Cavalry8th Regiment Infantry
1st Battalion Mountaineers