Department of New Mexico

The Department of New Mexico was a department of the United States Army during the mid-19th century. It was created as the 9th Department, a geographical department, in 1848 following the successful conclusion of the Mexican-American War, and renamed Department of New Mexico in 1853. It had to contend with an invading Confederate force during the New Mexico Campaign of the American Civil War from mid-1861 to early 1862, then with Apache tribes during the remainder of the conflict. It was merged into the Department of California after the end of the war as the District of New Mexico.

The Department of New Mexico was created from the existing 9th Department on October 31, 1853, administering the defense of the geographical areas now Arizona and New Mexico. When the Civil War started in April 1861, the commander of the department, Colonel William W. Loring, resigned on June 11 to join the Confederate army and was succeeded by Colonel Edward R.S. Canby of the 10th U.S. Infantry. Canby was ordered to send all of his regular infantry to Kansas and raise two New Mexico regiments as replacements; however, Canby was reluctant to do so, both because he feared a Confederate invasion from Texas and also he didn't trust the local population, which he suspected of disloyalty.

The first Confederates to invade the department did so in July 1861. Lieutenant Colonel John Baylor, commander of a battalion of the 2nd Texas Mounted Rifles, moved into the territory on July 23 and by the next evening had arrived outside of Fort Filmore, near the settlement of Mesilla. He planned to take the fort by surprise attack, but two Confederate deserters alerted the Union garrison to his plans; instead, the next morning Baylor moved into Mesilla. In the afternoon, the Union commander, Major Isaac Lynde attempted to drive out the Confederates but failed; feeling that his position was hopeless, Lynde then tried to retreat northward to Fort Stanton. However, the Union column quickly lost its cohesiveness during the hot daylight hours, so that when it reached San Augustine Springs Lynde reported that not "more than 100 men of the infantry battalion" could offer effective resistance. When Baylor arrived at the springs near midday, Lynde surrendered his command without further fighting. Lynde would be cashiered from the army in November for this surrender, which was seen throughout the North as needless and cowardly. Due to Lynde's surrender, several forts in southeastern New Mexico were abandoned, which gave the local Apaches an opportunity to raid local settlements. Baylor issued a proclamation declaring the part of New Mexico south of the 34th parallel to be the Confederate Territory of Arizona, with himself as governor.

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