Santa fe trail
Fort Union was one of a series of Army outposts near the Santa Fe Trail and was located at the western junction of the Dry and Mountain Routes. Its function evolved over time. Originally, it was supposed to police traffic on the Santa Fe Trail and to project federal military authority in New Mexico Territory, which had recently been won from Mexico. In the Civil War, troops stationed there prevented a Confederate invasion of the High Plains from the Rio Grande Valley via the Glorieta Pass. During the ensuing Indian Wars, Fort Union became an ever larger, ever more significant overland supply base before the advent of rail transportation (Weiser).
Fort Union grew in three phases. The first phase dated from 1851, a year after the Compromise of 1850 that organized New Mexico and Utah territories and admitted California to the Union as a free state. The second phase was a star-shaped earthwork fortification, finished early in 1862, which was located east of the original encampment. It was never the site of a battle. Instead, the decisive battle for control of the Southwest took place southwest of the fort itself toward Santa Fe in March of 1862. The so-called star fort was supposed to be out of range of cannon fire from the bluffs on the west bank of Wolf Creek, but test rounds fired in the summer of 1862 easily overshot the fort (U.S. National Park Service, Second Fort Union).
[The Fort Union of New Mexico territorial days should not be confused with the earlier American Fur Company operation at the junction of the Yellowstone and Missouri Rivers on the border of present-day Montana and North Dakota. Fort Union in New Mexico is more nearly contemporaneous with Fort Buford there.]
Many Indian nations supported factions that took advantage of the distraction of the Civil War to disrupt commerce throughout the Southwest while regular army units were withdrawn to fight in the Southeast. Until well after the end of that conflict, the defense of commerce along the Santa Fe Trail and throughout the High Plains and Sangre de Christo Mountains fell mainly to local New Mexico volunteer armed forces supplied from Fort Union (Sperry, Oliva).
Hearths and chimneys, foundations, pavement, and porch abutments are nearly all that remain of the massive third and final phase of development at Fort Union, which was started in 1863 and required six years to complete at a cost of over a million dollars (Sperry). In its day it was the largest military outpost west of the Mississippi River (U.S. National Park Service, Second Fort Union). Its main function was logistics, and, when the railroad arrived in Watrous in New Mexico Territory in 1879, Fort Union was eclipsed and made superfluous to the Army's needs. Fort Union no longer functioned as a supply depot after 1883 (Sperry).
In 1891, Fort Union was abandoned and fell into ruin.
Tin roofing, copper flashing, lead pipes, hardwood flooring, and milled doors and windows were quickly looted from the site (Oliva).
That year witnessed the deaths of General John C. Frémont and Sitting Bull, and General William Tecumseh Sherman was not far behind. Sir Richard F. Burton also passed away in 1890. Burton was a world famous British explorer who visited Salt Lake City on the eve of the Civil War probably as a spy. In 1861, he wrote a book, The City of the Saints, about that journey.