Banner image: Third Fort Union Military Prison, courtesy of the Fort Union National Monument
First situated near the junction of the Mountain and Cimarron Branches of the Santa Fe Trail, Fort Union (1851–1891) was one of the largest military installations in the New Mexico Territory. The location of the fort shifted three times during its commission (1851–1861, 1861–1862, 1862–1891). Notably, the second installation was an earthen star fort. Once the central supply hub for New Mexico posts, the third iteration of the fort waned after the arrival of the railroad in 1879.
Soldiers from Fort Union joined forces with New Mexico and Colorado Volunteers and headed south to meet the Confederate Army for the Battle of Glorieta Pass (March 26–28, 1862). It turned out to be the decisive battle in the New Mexico Campaign during the Civil War in the West.