|Territory of Arizona|
|Organized incorporated territory of the United States|
|New Mexico territories, showing existing counties.|
|Government||Organized incorporated territory|
|-||1863–1866||John Noble Goodwin|
|-||1909–1912||Richard Elihu Sloan|
|Legislature||Arizona Territorial Legislature|
|-||Arizona Organic Act||February 24, 1863|
|-||Statehood of Arizona||February 14, 1912|
The Arizona Territory was an organized territory of the United States that existed between 1863 and 1912, when the state of Arizona was admitted to the US. The territory was created after numerous debates about splitting the New Mexico Territory. During the American Civil War, the United States and the Confederate States had different motives for dividing the New Mexico Territory. Each claimed a territory named Arizona that was a portion of the former New Mexico Territory. The two Arizona territories played a significant role in the western campaign of the Civil War.
After the expansion of the New Mexico Territory in 1853 by the Gadsden Purchase, proposals for a division of the territory and the organization of a separate Territory of Arizona in the southern half of the territory were advanced as early as 1856. The first proposals for the Arizona Territory were not based on the current north-south division, but rather a division along an east-west line.
The first proposal dates from a conference held in Tucson that convened on August 29, 1856. The conference issued a petition to the U.S. Congress, signed by 256 people, requesting organization of the territory and elected Nathan P. Cooke as the territorial delegate to Congress. In January 1857, the bill for the organization of the territory was introduced into the United States House of Representatives, but the proposal was defeated on the grounds that the population of the proposed territory was yet too small. Later a similar proposal was defeated in the Senate. The proposal for creation of the territory was controversial in part because of the perception that the New Mexico Territory was under the influence of southern sympathizers who were highly desirous of expanding slavery into the southwest.
In February 1858, the New Mexico territorial legislature adopted a resolution in favor of the creation of the Arizona territory, but with a north-south border along the 109th meridian, with the additional stipulation that all the Indians of New Mexico would be removed to northern Arizona.
In April 1860, impatient for Congress to act, a convention of 31 delegates met in Tucson and adopted a constitution for a provisional territorial government of the area south of 34 degrees north. The delegates elected Lewis Owings as provisional governor.
At the outbreak of the Civil War, sentiment in the territory was in favor of the Confederacy. Territorial secession conventions were called at Mesilla and Tucson in March 1861 that adopted an ordinance of secession, established a Provisional Confederate Territory of Arizona with Owings as its governor, and petitioned the Confederate Congress for admission.
The Confederacy regarded the territory as a valuable route for possible access to the Pacific Ocean, with the specific intention of capturing California. In July 1861, a small Confederate force of Texans under the command of Lieutenant Colonel John R. Baylor assaulted Fort Fillmore at Mesilla in the eastern part of the territory. After the fort was abandoned by the Union garrison, Baylor's force cut off the fleeing Union troops and forced them to surrender. On August 1, Baylor issued a "Proclamation to the People of the Territory of Arizona", taking possession of the territory for the Confederacy, with Mesilla as the capital and himself as the governor. Baylor's subsequent dismantling of the existing Union forts in the territory left the white settlers at the mercy of the Apache, who quickly gained control of the area and forced many of the white settlers to seek refuge in Tucson.
On August 28, a convention met again in Tucson and declared that the territory formed the previous year was part of the Confederacy. Granville H. Oury was elected as delegate to the Confederate Congress. Oury drafted legislation authorizing the organization of the Confederate Territory of Arizona. The legislation passed on January 13, 1862, and the territory was officially created by proclamation of President Jefferson Davis on February 14.
The following month, in March 1862, the U.S. House of Representatives, now devoid of the southern delegates and controlled by Republicans, passed a bill to create the United States Arizona Territory using the north-south border of the 107th meridian. The use of a north-south border rather than an east-west one had the effect of denying a de facto ratification of the Confederate Arizona Territory. The house bill stipulated that Tucson was to be the capital. The final bill passed the Senate in February 1863 without the Tucson-as-capital stipulation, and was signed into law by President Abraham Lincoln on February 24, the date of the official organization of the US Arizona Territory. The first capital was at Prescott, in the northern Union-controlled area.
The boundaries for the original territory, if they had kept their same size, would make Las Vegas part of Arizona. However, in 1866, the northwestern section was annexed to the state of Nevada, and the territory maintained its current size. The following year, the capital was moved to Tucson, and in 1889 it was moved to Phoenix.
The territory was admitted to the Union as the 48th state on February 14, 1912.
PROCLAMATION TO THE PEOPLE OF ARIZONA 
I, JOHN N. GOODWIN, having been appointed by the President of the United States, and duly qualified, as Governor of the TERRITORY OF ARIZONA, do hereby announce that by virtue of the powers with which I was invested by an act of the Congress of the United States, providing a temporary government for the Territory. I shall this day proceed to organize said government. The provisions of the act, and all laws and enactments established thereby, will be enforced by the proper Territorial officers from and after this date.
A preliminary census will forthwith be taken, and thereafter the Judicial Districts will be formed, and an election of members of the Legislative Assembly, and the other officers provided by the Act be ordered.
I invoke the aid and cooperation of all Citizens of the Territory in my efforts to establish a government whereby the security of life and property will be maintained throughout its limits, and its varied resources be rapidly and successfully developed.
The Seat of Government will, for the present, be at or near Fort Whipple.
Signed at Navajo Springs, Arizona
December 29, 1863
By the Governor: Richard C. McCormick, Secretary of the Territory.
- American Civil War, 1861–1865
- Arizona Territory (CSA), 1861–1862
- Apache Wars, 1851–1886
- Gadsden Purchase, 1853
- Governors of the Territory of Arizona
- Historic regions of the United States
- History of Arizona
- James Reavis, The "Baron of Arizona"
- Mexican-American War, 1846–1848
- Navajo Wars, 1846–1865
- Territorial evolution of the United States
- Territory of Spain that encompassed land that later became part of the Territory of Arizona:
- States of Mexico that encompassed land that later became part of the Territory of Arizona:
- U.S. territories that encompassed land that later became part of the Territory of Arizona:
- U.S. states that encompass land that had once been part of the Territory of Arizona:
- Wagoner p. 32–33 & front piece
- Cheek, Lawrence W. (1995). Arizona. Oakland, CA: Compass American Guides. ISBN 1-878867-72-5.
- Cunniff, M.G. (January 1906). "The Last of the Territories". The World's Work: A History of Our Time XI: 7108–7119. Retrieved 2009-07-10.
- Sheridan, Thomas E. (1995). Arizona: A History. Tucson, AZ: The University of Arizona Press. ISBN 0-8165-1515-8.
- Wagoner, Jay J. (1970). Arizona Territory 1863–1912: A Political history. Tucson: University of Arizona Press. ISBN 0-8165-0176-9.