New Mexico Territory in the American Civil War

The New Mexico Territory, which included the areas which became the modern U.S. states of New Mexico and Arizona as well as the southern part of Nevada, played a role in the Trans-Mississippi Theater of the American Civil War. Both Confederate and Union governments claimed ownership and territorial rights over it. In 1861 the Confederacy claimed the southern tract as its own Arizona Territory and waged the ambitious New Mexico Campaign in an attempt to control the American Southwest and open up access to Union California. Confederate power in the New Mexico Territory was effectively broken after the Battle of Glorieta Pass in 1862. However, the territorial government continued to operate out of Texas, and Confederate troops marched under the Arizona flag until the end of the war. Additionally, over 8,000 troops from New Mexico Territory served the Union.

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 east-west scheme, but rather a north-south division. The proposals arose from concerns about the effectiveness of the territorial government in Santa Fe to administer the newly acquired southern portions of the territory.

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.

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