Colorado History: 10 Facts They Kept Classified for Decades
The Centennial State has a habit of burying its most important stories. Here’s what the textbooks left out.
There is a particular kind of historical amnesia that isn’t accidental. It isn’t the result of lost records or the simple passage of time. It is the deliberate, sometimes legally enforced suppression of events that powerful people — governments, corporations, military commanders — found inconvenient to remember. Colorado has more than its share of these buried stories.
The state that markets itself on mountain grandeur and frontier spirit was also the site of a nuclear weapons factory operating within commuting distance of a major American city. It witnessed one of the most consequential labor atrocities of the 20th century. It built an entire city for Japanese Americans in a matter of weeks, then tried to forget it existed. And it became the first state in the American West where women cast ballots in a presidential election — 27 years before the rest of the country caught up.
What follows is not a complete history. It is, instead, a corrective — the kind of history that deserves to be read alongside whatever you learned in school.
Rocky Flats: The Nuclear Secret 16 Miles From Downtown Denver
Of all the hidden histories in Colorado, none is more disorienting than Rocky Flats.
From 1952 to 1989, the Rocky Flats Plant manufactured plutonium triggers — the cores that initiate the chain reaction in a thermonuclear weapon — just 16 miles northwest of downtown Denver. At its peak, the facility produced between 1,000 and 2,000 “pits” per year. The workers who built them lived in Denver suburbs. Their children attended Denver schools. Most of their neighbors had no meaningful idea what was happening behind the perimeter fence.
What residents did not know, and what federal authorities worked methodically to conceal, was the scale of contamination surrounding the site. Plutonium-239 has a half-life of 24,100 years. Fires at Rocky Flats in 1957 and 1969 — both serious enough to warrant alarm — dispersed radioactive material into the surrounding environment. Soil testing conducted decades later found plutonium contamination at levels that, had they been discovered at the time, would have triggered immediate public health responses.
Author Kristen Iversen, who grew up in a subdivision near Rocky Flats, documented the plant’s history with meticulous precision in her book Full Body Burden. Her account captures something that raw data cannot: what it means to discover, as an adult, that your childhood backyard sat downwind from a nuclear weapons facility. In 1989, the FBI and EPA conducted a joint raid on Rocky Flats — a federal law enforcement agency raiding another federal facility — on suspicion of illegal hazardous waste disposal. The plant closed permanently that same year.
The cleanup that followed cost approximately $7 billion and took a decade to complete. Parts of the former site are now open as a national wildlife refuge. The prairie dogs, apparently, do not read the soil reports.
The Sand Creek Massacre: A Village Under an American Flag
On the morning of November 29, 1864, Colonel John Milton Chivington led approximately 700 U.S. volunteer soldiers to a Cheyenne and Arapaho encampment along Sand Creek in southeastern Colorado. What he found was a village that had been explicitly told it was under U.S. government protection. Chief Black Kettle had an American flag flying above his lodge — a symbol, given to him by federal officials, intended to signal precisely that assurance.
Chivington attacked anyway.
The death toll has been debated for more than a century, with estimates ranging from 150 to over 500 men, women, and children killed. What is not seriously disputed is the character of what followed. Congressional investigations conducted in 1865 documented mutilations and atrocities committed by Chivington’s men that are difficult to summarize in neutral language. The investigators used words like “barbarous” and “cowardly.”
Chivington was forced to resign his military commission. No criminal charges were ever filed. He later moved to Cincinnati, worked as a newspaper editor, and died in Denver in 1892 at the age of 70 — a free man.
The debate over whether Chivington should have faced criminal prosecution is not merely academic. It touches directly on questions of command responsibility, the legal status of treaty protections, and the relationship between military authority and civilian accountability — questions that remained unresolved at Sand Creek and have echoed through American military history ever since.
The Sand Creek Massacre National Historic Site was established by Congress in 2000. It took 136 years.
Ludlow, 1914: When Eleven Children Died in a Tent Colony
The Ludlow Massacre is one of the most significant events in American labor history, and it is among the least taught.
By 1913, the Colorado coal fields were among the most dangerous workplaces in the United States. Workers employed by Colorado Fuel and Iron — a company in which John D. Rockefeller Jr. held controlling interest — labored under conditions that included company-owned housing, company scrip instead of wages, and systematic intimidation of union organizers. When the United Mine Workers called a strike in September 1913, approximately 11,000 miners walked out.
The evicted miners and their families set up tent colonies across the region. The largest was at Ludlow, near Trinidad.
On April 20, 1914 — the day after Easter — Colorado National Guard troops and company-hired guards opened fire on the colony with rifles and a machine gun. That night, the tents were set alight. Beneath one tent, thirteen people — two women and eleven children — were found suffocated in a pit they had dug to shelter from the gunfire.
The death toll across the Ludlow Massacre and the ten-day armed uprising that followed reached approximately 75 people.
Congressional hearings placed significant responsibility on Rockefeller Jr., who had maintained strict control over company labor policy while publicly professing ignorance of conditions in the field. The testimony transformed Rockefeller’s public reputation and contributed, in ways historians still debate, to his subsequent philanthropy and support for industrial relations reform.
No one was convicted of any crime related to the Ludlow Massacre.
Colorado Women and the Vote: 1893, Not 1920
When the 19th Amendment to the U.S. Constitution granted women the right to vote in federal elections in 1920, Colorado women had already been casting ballots in presidential elections for 27 years.
In 1893, Colorado became the second state in the union — after Wyoming — to grant women full voting rights by popular referendum. Male voters approved the measure. It was not a close result: the margin was approximately 6,000 votes in favor.
This is worth dwelling on. Women voted in Colorado’s 1894 elections, sent three women to the state legislature that same year, and participated in every subsequent election cycle for nearly three decades before the constitutional amendment made their experience the national standard. The state’s early adoption influenced the broader suffrage movement significantly, providing both a practical model and a rhetorical argument that advocates used in other states.
Amache: A City Built in Weeks
In the spring of 1942, the U.S. government began construction of the Granada War Relocation Center — known as Amache — on the high plains of southeastern Colorado. The facility was designed to house Japanese Americans forcibly removed from the West Coast under Executive Order 9066.
At its peak, Amache held more than 7,300 people, making it briefly Colorado’s tenth largest city. It had its own schools, hospital, post office, and newspaper. It was also, by legal definition, a prison. Residents had not committed crimes. They had Japanese ancestry.
What makes Amache unusual within the broader internment story is what its residents did despite their circumstances. Amache men enlisted in the U.S. military in significant numbers; many served with the 442nd Regimental Combat Team, which became the most decorated unit of its size in American military history. The community maintained institutions, educated children, and cultivated an internal civic life under conditions of deliberate humiliation.
Amache was designated a National Historic Site in 2022. Preservation and archaeological work at the site continues.
The Denver Mint’s Secret WWII Production
The Denver Mint, established in 1863 during the height of the Colorado gold rush, is one of the most recognizable institutions in the state. What is less widely known is that during World War II, the facility’s operations extended well beyond currency production.
The Mint’s secure facilities, skilled workforce, and existing infrastructure made it a logical candidate for wartime manufacturing work that required precision and discretion. The full scope of classified production has been partially but not completely documented in the decades since — a reminder that even the most familiar civic institutions can carry classified histories.
The Pattern Beneath the Stories
Taken individually, each of these histories is remarkable. Taken together, they reveal something structural about how power operates in American life — and about which stories get preserved.
The communities most harmed by the events at Sand Creek, Ludlow, Rocky Flats, and Amache were communities with limited political power at the time: Indigenous nations, immigrant laborers, Japanese Americans, working-class families living downwind of federal weapons facilities. The suppression of their histories was not coincidental. Inconvenient truths tend to stay buried longest when those most affected have the fewest resources to insist on remembrance.
Colorado’s willingness, in recent decades, to excavate these histories — through the Sand Creek historic site, the Amache designation, the Rocky Flats cleanup and documentation, and the ongoing scholarly work of writers like Kristen Iversen — represents something genuinely important. It is not redemption. It is not sufficient. But it is the beginning of an honest accounting, and honest accounting is where all serious history starts.
The question worth asking, after absorbing any of these stories, is not only how did this happen? It is: what is being buried right now, and why?
The Sand Creek Massacre raises one of the most persistent unresolved questions in Colorado history: Colonel Chivington attacked a village flying an American flag under U.S. government protection, resigned his commission, and died without facing criminal charges. Whether that outcome represents justice, institutional failure, or something more complicated is a question historians and legal scholars continue to debate. It is also a question worth considering for yourself.
