New Mexico Territory in the American Civil War

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The New Mexico Territory, comprising what are today the U.S. states of New Mexico and Arizona, as well as the southern portion of Nevada, played a small but significant role in the trans-Mississippi theater of the American Civil War. Despite its remoteness from the major battlefields of the east, and its being part of the sparsely populated and largely undeveloped American frontier, both Confederate and Union governments claimed ownership over the territory, and several important battles and military operations took place in the region. Roughly 7,000-8,000 troops from the New Mexico Territory served the Union, more than any other western state or territory.^[1][2]

In 1861, the Confederacy claimed the southern half of the vast New Mexico Territory 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-held California. Confederate power in the New Mexico Territory was effectively broken when the campaign culminated in the Union victory at the Battle of Glorieta Pass in 1862. Although the Confederacy never attempted another invasion of the region, its territorial government continued to operate out of Texas, with Confederate troops marching under the Arizona flag until the end of the war.