During the centennial of the American Civil War, we learned at school that Colorado’s pioneer miners took part in a significant battle on Mar. 26, 1862, one that historians called "the Gettysburg of the West." It happened at Glorieta Pass, a few miles east of Santa Fe in New Mexico. Volunteers from Colorado Territory marched hard and fast from Denver, arriving just in time to stop Confederate rebels from crossing the Rocky Mountains, taking Fort Union, and capturing the gold fields of Colorado before marching west to California. The gold would have allowed the Confederacy to buy much-needed supplies, and with Pacific seaports under their control, the Rebels would have more ways to evade the Union blockade.

Now, 50 years later, a modern history book (America Aflame by David Goldfield) tells me that "The Battle of Glorieta Pass makes it into most Civil War books primarily because readers in the Southwest and California want to be included in the great American drama. So here it is. But the battle was meaningless. The Confederacy's designs on California were far-fetched and ill-conceived."

Before we try to decide how important this particular battle was –– or wasn't –- we need to remember that even if very little of the Civil War was fought in our West (the western theater of that war was the Mississippi Valley), there's a good argument to be made that the Civil War was ultimately about controlling our region. Southern states seceded in response to the election of Abraham Lincoln, who had pledged not to interfere with slavery where it already existed. But he was steadfast about "no expansion of slavery to the territories" (i.e., our West), and the South couldn't abide that.

Texas seceded and joined the Confederacy on Feb. 2, 1861. Henry H. Sibley, an American Army officer stationed in New Mexico, joined the Confederate forces in Texas. Sibley proposed a Confederate invasion of New Mexico; President Jefferson Davis approved and put Sibley in charge of the campaign. With 3,500 men, he started north up the Rio Grande on Feb. 7, 1862, from Fort Bliss near El Paso.

Sibley's plan was to march up the Rio Grande Valley, capturing federal supplies of food and munitions along the way to Santa Fe. Then he'd swing east over Glorieta Pass to take Fort Union, near present-day Las Vegas, before marching north to seize the Colorado gold fields. The soldiers would then march west on the Oregon Trail to take California, where the Confederates believed there were plenty of Southern sympathizers who would augment Sibley's force.

It was an 1862 version of "Mission Impossible." Almost immediately, the plan went awry. The New Mexicans refused to sell supplies to the Texans, who hesitated to just take what they wanted because they still hoped to gain Confederate allies in the region.

The outnumbered U.S. forces fell back before Sibley's northbound Texans. But the Union troops burned their supplies before they retreated, keeping them out of Confederate hands. Meanwhile, New Mexico asked for help from neighboring Colorado Territory, where Gov. William Gilpin organized the First Regiment of Colorado Volunteers. To cover the costs, Gilpin issued $375,000 in unauthorized drafts on the federal treasury (an act which later cost him his job).

The Colorado force of 1,342 officers and men marched south at a brisk pace, covering 400 miles in 14 days to reach Fort Union on March 10, 1862. Union and Rebel forces met two weeks later, about 25 miles east of Santa Fe at Glorieta Pass. The Confederates had the edge at first. Then, as one Texan put it, the Federals climbed into the rocks above and started "shooting us down like sheep." The Federals were "regular demons, upon whom iron and lead had no effect, in the shape of Pikes Peakers from the Denver City gold mines."

The battle was technically a Confederate victory, since the Texans still held the field when the Union forces began to retreat. However, about 400 federal soldiers fell upon the Confederate supply train in the rear, setting it on fire and killing the horses and mules. Without supplies or transportation in hostile and often barren territory, Sibley could not advance on Fort Union. He had to retreat back to El Paso.

Did the Battle of Glorieta Pass save the West for the Union? What if the Confederates had crossed the mountains and marched north into Colorado? They still would have been a long ways from Fort Bliss without supplies in hostile territory, for Colorado was Union country with few Confederate sympathizers. Transporting Rocky Mountain gold to the Confederate capital in Richmond, Va., would have been extremely difficult, and if necessary the Union could have marched a force west from Fort Leavenworth, Kan. -- the nearest large Union military installation -- to overwhelm Sibley's Texans in Colorado.

Both Glorieta and Gettysburg were three-day battles, both resulted from a Confederate invasion of Union territory, and both ended as Union victories. But the scale of the two battles was vastly different. The estimated total killed, wounded and captured on both sides in three days at Glorieta came to 331 -- not even a rounding error compared to the estimated 45,000 who died in three days at Gettysburg.

Nonetheless, in 1993, the Glorieta battlefield was one of 10 military action sites (out of about 10,500) identified by the national Civil War Sites Advisory Commission as a scene of major war-changing significance that was worthy of preservation by Congress. Glorieta was ranked right up there with Gettysburg and Antietam.

About 20 percent of the battleground -- approximately a square mile known as Pigeon's Ranch -- is now protected as part of the Pecos National Historical Park. Other portions of the battlefield are in private hands, though, so there's an effort under way to expand the national historic park to include that ground.

For my part, whenever my Texas brother-in-law starts talking about how the Lone Star State should reclaim the Rocky Mountain territory it ceded in 1850, I can respond with, "Hey, we kicked your ass the last time you tried to invade. Bring it on."

Ed Quillen writes from Salida, Colorado.