In the 1860's news of the Civil
War and also troop conflict reached Mesilla. Colonel Baylor, Commander of Confederate troops, arrived from Texas and encountered little resistance in the Mesilla Valley.
On July 25, 1861, when Colonel Baylor and his 220 Texas Mounted Rifles entered Mesilla, the Union troops abandoned Fort Fillmore. They
surrendered to the Confederate troops at San Augustin Spring, north-west of Mesilla, two days later. Colonel Baylor set up his immediate
headquarters on Calle Principal, off the Plaza in Mesilla, and raised the Confederate flag at the Confederate capitol building (on Calle de Guadalupe
, where the old theater is today). He established the name of the Confederacy, the short-lived territory of Arizona, with Mesilla as its capital.
The Grand Plaza, where the Confederate troops established their headquarters, was located in the area of the school. After the Battle of
Glorieta in March of 1862, being short of supplies, the Confederate troops retreated to Texas. This ended the Civil War conflict in New Mexico.