District of Arizona was a subordinate district of the Department of New Mexico territory created on August 30, 1862 and transferred to the Department of the Pacific in March 1865.
Headquarters at Franklin, Texas, then Mesilla Post until 1864.
Headquarters Prescott, Arizona
On July 27, 1865 the Military Division of the Pacific was created under Major General Henry W. Halleck, replacing the Department of the Pacific, consisting of the Department of the Columbia and the expanded Department of California, that absorbed the District of Southern California and that consisted of the States of California and Nevada and the District of New Mexico in the Territory of New Mexico and District of Arizona in the Territory of Arizona.
Arizona remained a district until it became the Department of Arizona under the Military Division of the Pacific on April 15, 1870. Colonel George Stoneman transitioned from district to department commander, serving until June 4, 1871. The new department consisted of Arizona Territory and California south of a line from the northwest corner of Arizona to Point Conception so as to include most of Southern California.