More Arizona Trivia-Where Was the Western Most Battle Fought in the Civil War?

Yes, Arizona.  It is called the battle of Picacho Pass. It happened near Picacho Peak which is located between Phoenix and Tucson.  On April 15, 1862. It was fought between a Union Calvary patrol from California and a party of Confederate Pickets from Tucson.

Twelve Union Calvary troopers and one scout of the 1st California Cavalry, were conducting a sweep of the Picacho Peak area, looking for Confederates reported to be nearby. The Calvary were under orders not to engage them, but to wait for the main column to come up. However, their patrol surprised and captured three Confederate pickets. It failed to see seven other Confederate soldiers before they opened fire. During the bloody skirmish that followed, two Union soldiers were killed and three others wounded. In 1864, the Union organized its own territory of Arizona, dividing New Mexico along the state's current north-south border, extending control southwards from the provisional capital of Prescott.