Eleven states seceded from the Union in 1861, forming the Confederate States of America and sparking the American Civil War. While the South had focused on building an agrarian society, the North had invested in industrial expansion and was better equipped for military campaigns. The Confederacy was desperately short of raw materials for war productions, as well as rations, uniforms and many other military provisions. Many materials had to be imported and often paid for in gold. As a result gold and seaports became very important to the southern cause.
The West had both seaports and gold, and the Confederates wanted them. In the summer of 1861 Confederate forces in Texas moved north through New Mexico, targeting garrisons along the way, raiding them of supplies. Their main target was Fort Union, the major supply depot of the Southwest and largest fort on the frontier. Located 28 miles north of Las Vegas, New Mexico, the post contained the troops and supplies necessary to support the Union cause in the West.
By March of 1862 Confederate forces had seized the capital at Santa Fe and were on their way north for Fort Union when they were met at Apache Canyon at Glorieta Pass (about 30 miles north of Santa Fe) by Union soldiers and both New Mexico and Colorado volunteers who had mustered up for the westernmost campaign of the American Civil War.