Colorado’s role in the American Civil War (1861–65) was part of a broader geopolitical contest: control of the American Southwest. The war began in 1861, just two years after the Colorado Gold Rush and mere months after Congress established the Colorado Territory. Although the territory was largely pro-Union, the Confederacy and its local sympathizers immediately realized Colorado's strategic and monetary value and wanted to take advantage of it.
Federal troops from Colorado turned back the Confederate invasion in New Mexico, ensuring that the Rocky Mountain gold mines remained under US control. This paved the way for further conquest and development in Colorado and the rest of the West. The Civil War had wide-reaching effects, especially on Indigenous people. The Homestead Act, passed during the war in part to promote free labor over slave labor in western territories, was a direct assault on Indigenous people’s sovereignty that increased tensions between whites and Native nations. Before the war was even over, Union troops committed the Sand Creek Massacre, one of the worst atrocities on US soil and an event that would influence future conflicts between Americans and Indigenous people.
As it has elsewhere, the Civil War left a complicated legacy in Colorado, one that laid the foundation for the successes and struggles of the state to the present day.
Origins
The tensions that eventually placed Colorado in the western theatre of the Civil War were tied to the same issue that caused the war: the expansion of slavery. In 1848 the Treaty of Guadalupe Hidalgo ended the Mexican-American War and added almost one million square miles to the United States. Southern politicians and elites wanted to expand slavery into this newly acquired land. The California Gold Rush followed in 1849, leading to the Compromise of 1850: Congress admitted California into the Union as a free state but reinforced the Fugitive Slave Act to satisfy southern complaints. In 1853 President Franklin Pierce appointed Jefferson Davis as Secretary of War. In that role, Davis, who would later become president of the Confederacy, wanted to create a southern transcontinental railroad that would cross New Mexico on its way to California.
Meanwhile, the Colorado Gold Rush of 1858–59 had put the Rocky Mountains on the map for many Americans. The resulting influx of white gold seekers and the myriad enterprises accompanying them created a need for law and order. After establishing a treaty with the Cheyenne and Arapaho, the federal government organized Colorado Territory in February 1861, about a month and a half before the Confederates fired on Fort Sumter and ignited the Civil War in the east.
With the outbreak of war, gold in Colorado and California and the latter’s Pacific ports represented valuable prizes for the new Confederacy. To win those prizes, the Confederates would need control of the Santa Fé Trail, whose Mountain Branch followed the Arkansas River through Colorado before turning south over Raton Pass and into New Mexico. The trail was one of the major commercial routes in the West, and it was protected by Fort Union, the Army’s major supply depot north of Santa Fe. In addition, the scattered villages and towns of New Mexico territory were protected in the south by Fort Bliss near present-day El Paso, Texas, Fort Craig south of Albuquerque, and Fort Marcy at Santa Fe. The Confederate strategy was to invade north from Texas, take New Mexico and Colorado, and then turn west toward California.
Choosing Sides
The outbreak of war east of the Mississippi River led the US government to relocate federal troops from the West for service in the East. Some officers resigned from the US Army to fight for the Confederacy. One was Major Henry Hopkins Sibley, who resigned on May 13, 1861. Colonel William Loring, Commander of the Military Department of New Mexico, quit on the same day, leaving Lt. Colonel Edward R. S. Canby of the Tenth Infantry to command federal troops in New Mexico.
In 1860 Colorado had 30,000 non-Indigenous residents, 70 percent of whom were from northern states and territories. The territory was largely pro-Union. But as Colonel Canby begged for reinforcements, Territorial Governor William Gilpin explained that a “malignant secession element” of 7,500 Confederate sympathizers had to be controlled. In Denver City, Charley Harrison’s Criterion Bar was the pro-Confederacy headquarters, while other sympathizers from across the territory secretly gathered at Mace’s Hole north of Pueblo.
Harrison was eventually arrested, fined, and exiled from the territory. Scattered skirmishes and other clashes between Union- and Confederate-aligned Coloradans continued throughout the war, although no major battles were fought in the territory.
Battle Lines
In May 1861, Canby received orders to send four infantry companies from Colorado and New Mexico to Fort Leavenworth in eastern Kansas. He kept troops to garrison Albuquerque and Forts Craig, Marcy, Union, and Fort Garland in southern Colorado. In September, he appointed Kit Carson as Colonel of the First Regiment of New Mexico volunteers, newly recruited from the territory’s Hispano population. Canby left some troops at Fort Union to build an earthwork; the rest he sent to Albuquerque. But Sibley, now a Confederate Brigadier General, led an army out of Texas and up the Rio Grande, intending to take Colorado. Canby needed more troops.
He appealed to Gilpin for volunteer troops to replace and support his garrisons. Gilpin was newly appointed by President Abraham Lincoln. Before he left Washington for Colorado, Secretary of War Simon Cameron assured Gilpin that the federal government would cover the costs of raising troops to defend the territory. Upon arriving in Denver City in May 1861, Gilpin raised two companies of volunteers, which grew by August to become the First Regiment of Colorado Volunteers. He appointed Denver lawyer John Slough as Colonel.
With their own weapons and civilian clothes, the recruits assembled at Camp Weld along the South Platte River upstream from Denver City. Gilpin covered their expenses by issuing $375,000 in promissory notes, payable by the federal government, earning First Colorado the nickname “Gilpin’s Pet Lambs.” Treasury Secretary Salmon Chase refused to honor Gilpin’s promissory notes, and Denver merchants went to Washington to demand payment. Gilpin followed to explain his actions. The Treasury Department honored the notes, but President Lincoln fired Gilpin on March 18, 1862, and replaced him with John Evans.
Fortunately for Canby, Gilpin had other troops to send. Independent of the First Colorado, two companies of volunteers assembled in August at Cañon City, led by Captains Theodore Dodd and James Ford. In September, Gilpin ordered them to Fort Garland in the San Luis Valley. They arrived in December 1861 and mustered into federal service, rounding out Colorado’s federal forces.
Battle of Valverde
Sibley’s Confederate force entered New Mexico on February 7, 1862, with 2,515 men, most of them Texans, and fifteen artillery pieces. While in overall command, Sibley was derided by his soldiers as “a walking whiskey keg” who somehow managed to be sick in a wagon during every battle in New Mexico.
The wagon road from Fort Bliss to Santa Fe ran along the east side of the Rio Grande River. Fort Craig lay on the west side of the river. Canby had a garrison of 3,810 soldiers, a mix of regular US army troops, New Mexico militia volunteers, and Dodd’s company of Colorado troops. On February 21, 1862, Canby tried to block Sibley’s advance near the abandoned village of Valverde, resulting in a day-long battle that claimed more than 100 casualties on both sides.
Sibley’s men won the battle of Valverde, but Canby still had 3,000 men in a strong position, and the Confederates had to give up on the food and fodder in Fort Craig, provisions they had counted on for their advance.
Meanwhile, federal forces abandoned Albuquerque and Santa Fe, falling back up the Santa Fé Trail to Fort Union. The Texans occupied Santa Fe on March 10, 1862, and turned their sights on Fort Union. Acting Governor Lewis Weld of Colorado sent the First Colorado Volunteers to reinforce Fort Union’s garrison of 800 men. On March 11, the Volunteers arrived at Fort Union, which they found in a dangerous position. The fort was tilted toward the hills to the west, where Confederate artillery could shoot exploding shells straight into the star-shaped earthwork. Believing the only possible defense was offense, Colonel Slough outfitted and resupplied his men, marching them down toward Santa Fe on March 22, 1862.
Battle of Glorieta Pass
Slough led a combined force of 1,342 men, including assorted regulars and volunteers from Colorado and New Mexico. Unaware of the Union reinforcements, Confederate Major Charles Pyron probed forward from Santa Fe with a smaller battalion of 400 men and two six-pounder cannons. Slough sent an advance force of 418 infantry and cavalry, led by Major John Chivington, to try to find the Texans. On the night of March 25, the federals captured four Texans at Kozlowski’s Ranch, east of Glorieta Pass. Advancing west the next morning into Apache Canyon, Chivington captured thirty-two more Texans, opening the Battle of Glorieta Pass.
Pyron set up his cannons on the road in Apache Canyon but soon had to pull back as the Union forces threatened to surround his position. Pyron’s new position was behind an arroyo, spanned by a bridge that the Confederates burned. In front of his guns, with the arroyo at their front, Pyron’s cavalry formed a defense.
In the most dramatic moment in Colorado’s Civil War, Company F of the First Colorado mounted a cavalry charge, leaping its horses over the arroyo and rolling over the Confederate line. In hand-to-hand fighting, Pyron got his cannons away to the rear. Night fell, ending the fighting in Apache Canyon and the first day of the Battle of Glorieta Pass. The federals lost five killed and fourteen wounded. Of Pyron’s 420 men, four were killed, twenty wounded, and seventy-one taken prisoner, the costliest single day of battle in the New Mexico campaign.
The Texans withdrew to Johnson’s Ranch at the west end of Apache Canyon, and Chivington’s command pulled back for water to Pigeon’s Ranch at the east end. Both sides agreed to a truce for the night and prepared to repel an assault by the enemy the next day. Neither side attacked.
Chivington did move farther east, to Kozlowski’s Ranch, for more water. Slough arrived there at 11:00 pm with the rest of the regiment. Then, at 3:00 am on the 27th, Confederate Colonel Scurry reinforced Pyron, taking command of the now 1,000 men at Johnson’s Ranch. Unaware of Scurry’s arrival, Slough planned a two-pronged attack for the 28th. Chivington was to lead 490 men on a sixteen-mile march over the mesa that formed the southern flank of Apache Canyon. His guide would be New Mexican volunteers led by Lt. Colonel Manuel Chaves. As Slough fought the Confederates on the Santa Fé Trail, Chivington’s command would fall upon the Texans’ rear.
On the early morning of the 28th, the Colorado troops advanced, with Chivington’s command splitting off to the south just before Pigeon’s Ranch. At the same time, the Texans left their supplies behind at Johnson’s Ranch as they struck at the federals. At 11:00 am, the two forces met west of Pigeon’s Ranch and began a six-hour artillery duel, with infantry pushing against each other’s lines. Without Chivington, Slough had 850 men to Scurry’s 1,000. Outnumbered, the federal forces had to fall back to avoid encirclement by the Texan infantry slowly. The Union position was eventually forced back five miles to Kozlowski’s Ranch. By about 5 pm, the Texans held the field at Pigeon’s Ranch, and the day was a tactical victory for the Confederates.
However, in the meantime, Chivington’s command had arrived on the bluff above Johnson’s Ranch and found that the Texans had left the entire Confederate supply train undefended below them. At 4 pm, they swept down into the canyon, captured the guards, and destroyed eighty wagons, a cannon, all the Texans’ food and supplies, and 500 mules and horses. Freeing federal prisoners, the Colorado troops retraced their steps, arriving at Kozlowski’s Ranch at 10 pm on the 28th.
Slough was ordered to return to Fort Union, where he resigned, and Chivington took command. Casualty counts vary, but contemporary sources estimate that the federal troops lost forty-nine killed, sixty-four wounded, and twenty-one taken prisoner. On the Confederate side, Scurry reported thirty-six Texans killed, sixty wounded, and twenty-five captured.
Without food and ammunition, the Texans could go no farther. They retreated to Santa Fe, and then south to Albuquerque. They headed back to Texas, loosely pursued by federal forces. An afternoon sandstorm ended an inconclusive artillery duel at the village of Peralta on April 16. Canby saw no reason to engage the retreating Confederates, and the last defeated Confederates straggled into Texas on July 8.
Later Engagements
Meanwhile, now-Colonel Chivington was put in charge of the Military District of Colorado. The Colorado Volunteers shifted from patrolling for Confederates to patrolling for Indigenous parties who sought to repel the invaders from their homelands. In November 1862, the First Colorado was converted into cavalry. Chivington kept them in Colorado, centered on Fort Lyon (formerly Fort Wise), but that post’s commander sent some of the garrison east to Kansas. The First spent the rest of the war guarding wagon trails in Colorado and Kansas; in July of 1863, Major Ned Wynkoop led four companies to patrol the Oregon Trail all the way to Fort Bridger in southeastern Wyoming.
Dodd’s and Ford’s Companies of the Second Colorado arrived at Fort Lyon from New Mexico in April 1863, joining six companies recruited by Colonel Jesse Leavenworth; Theodore Dodd became second in command. On April 11, 1863, Lt. George Shoup and a recruiting party of eleven men encountered a camp of three Confederate “guerrillas” near present-day Colorado Springs, killing one, wounding one, and capturing the last. The War Department soon authorized a Third Colorado Infantry regiment. The Third Infantry later merged with the Second Infantry and was sent to Missouri to fight irregular enemy forces there. After outfitting as cavalry near St. Louis in December of 1863, Second Colorado deployed across Missouri, combatting Confederate guerrillas known as “bushwhackers.” Over the next year, the volunteers fought in several pitched battles as they defended St. Louis and Kansas City from advancing Confederates.
In Colorado, assorted pro-Confederate guerrillas tried to operate, but territorial troops and vigilantes hunted them down as outlaws.
From Saving the Union to Massacring the Innocent
In 1864 Governor Evans and Chivington wanted to remove the Cheyenne and Arapaho people from Colorado’s eastern plains. This objective arose from increased tensions after the 1851 Treaty of Fort Laramie was revised in 1861. The Homestead Act of 1862 gave white immigrants “free” land that many Cheyenne and Arapaho still considered theirs. Following the directives of the 1861 treaty, Moketaveto’s Cheyenne and Hossa’s Arapaho camped near Fort Lyon in November 1864. They had an American flag raised over the camp, indicating their allegiance to the treaty and distinguishing their camp from other warrior groups who resisted the new treaty.
In early June 1864, a party of Indigenous warriors—possibly Arapaho—killed a young family who worked for a homesteader on the plains outside of Denver. The murders were most likely reprisals from the earlier killing of an Indigenous man that day, but Denver residents blamed the Cheyenne and Arapaho. With a family killed and scattered attacks on wagons and homesteads occurring throughout the summer, Evans saw in the fears of the trespassing white population an opportunity to rid the territory of both the Cheyenne and Arapaho. He authorized Chivington to enlist a new Third Colorado Cavalry for 100 days, and Chivington, who hated Indigenous people as much as he hated Confederates, went on the warpath. On November 29, 1864, he found and attacked the peaceful Cheyenne and Arapaho camp at Fort Lyon, killing more than 200 women, children, and elders in what became known as the Sand Creek Massacre.
Praised as heroes in Denver, Chivington and the Third were seen as bloodthirsty murderers in the eastern United States. Chivington resigned to avoid a military court martial while war exploded across the plains. On January 7, 1865, 1,000 Cheyenne and Lakota fell on Julesburg, and on February 2, they burned the town before moving north out of Colorado. The so-called “Colorado War” resumed in March through July. President Andrew Johnson fired Evans over his role in precipitating Sand Creek.
Legacy
Colorado’s experience in the Civil War can best be described as a successful defense of empire. When the war started, the territory was essentially defenseless and held a vast amount of vulnerable wealth; as the war came to its doorstep, Coloradans mounted a furious and successful defense of that wealth, even as Confederate sympathizers sought to sabotage it from the inside.
With the successful defense of the gold fields came federal military activity on a scale never before seen in the territory. With Indigenous people already facing disease and starvation due to poorly understood and enforced treaties and the contempt of white settlers and politicians, the militarization of Colorado after the Civil War led to destruction and disaster for the Cheyenne, Arapaho, and eventually the Nuche (Ute people) who lived in the Rocky Mountains. Eventually, the Treaty of Medicine Lodge in 1867 forced Colorado’s Cheyenne and Arapaho to cede their remaining land in the territory and assigned them to reservations in Oklahoma.
Meanwhile, for Colorado’s invading American population, the Civil War had dried up eastern sources of capital needed to fund mining, even as it helped them feel more secure in what was still a fledgling territory. Foreign technology arrived with Nathaniel Hill’s smelter in 1867, reviving the mining industry. With North and South at peace, the transcontinental railroad was finished and linked to Denver in 1870. Emancipation and a growing mining economy caused Colorado’s Black population to increase substantially from 1870 to 1900.
Colorado achieved statehood in 1876. In 1898, as troops boarded trains in Denver to fight in the Spanish-American War, Union veterans lined one side of Seventeenth Street and Confederate veterans assembled on the other side. As a show of unity, they boarded the train together, seemingly burying the hatchet.
The past is still with us, of course. Despite the train station moment and other reconciliation between whites, the racism that brought the Civil War to Colorado has lingered in the state to the present. Redlining, or excluding Black residents from buying homes in certain neighborhoods, persisted throughout Denver and other cities, as did institutional discrimination in housing, education, and employment. Several Colorado towns, including Golden, Louisville, Loveland, and parts of Colorado Springs, were known at various times as “Sundown” towns—places where Black people were not welcome and would be run out of town at sundown. Police violence is still disproportionately aimed at Colorado’s Black residents and people of color.
The Sand Creek Massacre was later erroneously listed as a “battle” on the plaque of a statue commemorating Colorado’s Civil War veterans. Chivington’s actions were considered horrific even during his time, but the plaque remained, igniting controversy until activists removed the statue during the 2020 Civil Rights demonstrations in Denver. As of this writing, streets, university buildings, and even mountains once named for those associated with the Sand Creek Massacre have either been renamed or are being evaluated for renaming in an ongoing reconciliation process.
Referred to as the "Gettysburg of the West," the Battle of Glorieta Pass pitted Union troops from Colorado against Confederates from Texas. The battle took place south of Santa Fe, New Mexico, in the spring of 1862. Although it was a stalemate on the field, the Colorado troops destroyed the Confederate supplies, ending the Confederacy's ambition to take the western territories.Battle of Glorieta Pass
From 1909 to 2020, a statue honoring the Coloradans who fought in the American Civil War stood outside the State Capitol building in Denver. It incorrectly listed the Sand Creek Massacre, in which Colorado troops slaughtered more than 200 women, children, and elderly Indigenous people, as a "battle" in the war. Civil Rights protesters took down the statue during demonstrations against police abuses and institutional racism in 2020.Civil War Soldier Statue, Denver
