Fort Union on the Santa Fe Trail in New Mexico Also Had a Role in the Civil War

In 1851, the U.S. Army constructed a fort along the Santa Fe Trail in northeastern New Mexico territory. Fort Union, as it was called, was one of the more important such installations in the southwest, providing security along the trail as well as being a large supply depot for other forts in the region. For the first 10 years of its existence, the army carried out cavalry missions from Fort Union against Native American tribes as more American settlers and commerce traveled into and through the territory on the Santa Fe Trail.

That all changed after the Civil War began in 1861. The Confederacy, and in particular, Confederates in Texas began to take an interest in New Mexico territory, with some troops marching into southern New Mexico in the summer of 1861. At the time, Fort Union was essentially a village without fortifications and would be vulnerable to an attack by a large force, especially one that had artillery. Construction of a second fort began in August. This second Fort Union was about a mile east of the original fort, in a more defensible position on flat ground away from some bluffs. The fort was a star shaped earthen and timber fortification complete with bombproof shelters designed to withstand an attack from a sizable enemy force equipped with artillery. It was often referred to as the Star Fort due to its shape.

Second Fort Union, or Star Fort.

While the Federals were fortifying their position at Fort Union, Henry H. Sibley, a former U.S. Army officer who had served at Fort Union before resigning in June of 1861 to join the Confederate Army, was lobbying the Confederate government for a military operation to take New Mexico, and the rest of the southwest. Sibley’s ambitious plan was to organize and march an army into New Mexico from Texas with the goal of capturing New Mexico, and then continuing on to take the gold mines of Colorado before heading west to southern California and the Pacific Ocean. In order to supply this army, the plan relied on the capture of supplies in U.S. government and military installations; one of those with the greatest importance was Fort Union and its associated vast amount of supplies.

Map of Forts of the Southwestern U.S. Territories in 1861

Sibley, who was awarded a brigadier general’s commission, was given the go ahead to proceed with his plan and spent the summer and fall organizing his army at his base in San Antonio, Texas. Sibley marched late in the year, and in December his army began to enter New Mexico along the Rio Grande River at El Paso, Texas.

Sibley’s army defeated Union forces at the Battle of Valverde near Fort Craig in the Rio Grande valley in February 1862, but did not capture that well defended fort and its supplies. Marching north, the Confederates captured Albuquerque and Santa Fe in March, and then proceeded to the northeast for the purpose of capturing Fort Union and its vital supplies. Fort Union’s garrison consisted of some 800 U.S. Regulars and New Mexico and Colorado volunteers. They were reinforced on March 9th by the 1st Colorado Infantry under the command of Colonel John P. Slough. Slough took over command of Fort Union from Colonel Gabriel Paul on the basis of seniority, despite the fact that Paul was an over 20 year veteran of the Regular Army.

Slough was not about to wait for the enemy to come to him. Leaving a few hundred men at the fort, Slough took his 1st Colorado and others for a column with a total strength of 1340 and headed west on the Santa Fe trail. The two sides fought a three day battle on March 26th-28th at Glorieta Pass, resulting in a Union victory. The Battle of Glorieta Pass also put an end to offensive operations by the Confederates, who withdrew from New Mexico after their defeat and did not return for the rest of the war.

In August of 1862, construction of a third Fort Union complex next to the Star Fort was approved. The buildings for this version of Fort Union were made of adobe bricks set on stone foundations. This included officers quarters, enlisted men’s barracks, corrals, warehouses, a hospital, and other structures. The fort resumed its role in guarding the Santa Fe trail and as the primary supply depot for other military installations in the southwest. African American soldiers–most notably, the famed Buffalo Soldiers of the 9th U.S. Cavalry–were stationed at and operated from Fort Union after the Civil War.

With the arrival of the railroads in the late 1870s and into the 80s, the Santa Fe trail faded in importance as a transportation route. Operations against Native Americans in the region ended in the 1880s, and Fort Union closed in May of 1891. Over the years, people from nearby towns took parts of the buildings such as windows, etc. for their own use, eventually leaving the abandoned buildings as ruins.

Mechanics Corral Ruins Fort Union National Monument

Visiting Fort Union National Monument

In 1954, the site of Fort Union was preserved with the creation of Fort Union National Monument. The site is located on I-25 about 28 miles northeast of Las Vegas, New Mexico. Take Exit 366 at the town of Watrous to Highway 161, and head north about eight miles on 161. Fort Union is at the end of the road. Along the way, you can see wagon ruts from the Santa Fe trail; they are also visible at Fort Union itself.

Officers Quarters Ruins, Fort Union National Monument

There is a visitor center at the site. Two interpretive trails, a 1.6 mile and a half mile in length, wind around through the remaining adobe structures of the third fort and through the remnants of the Star Fort. There is no public access to the first fort site. There is no admission fee and the site is open every day except New Year’s, Thanksgiving, and Christmas Day.

Remnants of Second Fort Union Earthworks, Fort Union National Monument