Construction on the Transcontinental Railroad began on January 8, 1863 in Sacramento, when workers for the Central Pacific Railroad first broke ground for the track. Eleven months later, their counterparts in the Midwest—workers for the Union Pacific Railroad—began breaking ground in Omaha.

Racing to meet in the middle, they completed the project in 1869. With brute manpower, engineering savvy—and little in the way of heavy equipment—they conquered some of the nation’s most daunting terrain. The work included grading steep mountain faces, building bridges across vast canyons and blasting tunnels through solid granite.

It was widely viewed as an American triumph—the railroad vastly expanded America’s economy as it opened up opportunity in the American West. But there was also a dark side to the historic national project. The railroad was completed by the sweat and muscle of exploited labor, it wiped out populations of buffalo, which had been essential to Indigenous communities, and it extended over land that had been unlawfully seized from tribal nations.

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While the transcontinental Railroad enjoyed wide support—from President Abraham Lincoln, Congress and business leaders and investors—finding enough workers among America’s white laboring class to undertake the grueling and hazardous work proved challenging. Many Irish immigrants and other white laborers who moved west chose instead to pursue farming or mining.

In January 1865, Central Pacific published an ad seeking 5,000 railroad workers. Several hundred white workers responded, according to historians Gordon H. Chang and Shelley Fisher Fishkin in their book The Chinese and the Iron Road: Building the Transcontinental Railroad, but the job required many more hands. So railroad companies began recruiting abroad, focusing particularly on China.

The first Chinese railroad workers (a team of 21 men) arrived in the United States in 1864; ultimately, it’s estimated that some 20,000 Chinese laborers participated in the project, making up the majority of the workforce. Most came from China’s southern Guangdong province, fleeing their country’s Opium Wars. They were joined in the effort by African Americans, Irishmen and smaller numbers of Native Americans and Mormons (now referred to as members of the Church of Jesus Christ of Latter-day Saints).

The treatment and working conditions of each group varied widely. According to researchers at Stanford University’s Chinese Railroad Workers in North America Project, Chinese laborers earned between half and two-thirds of what Euro-American laborers did, and had to pay for their food. In the summer of 1867, thousands of Chinese workers organized the largest labor stoppage in America up to that date to demand both equal pay and better working conditions. Railroad bosses ultimately broke the strike by withholding food rations and threatening violence, and the workers’ demands were denied. But their pushback showed that the Chinese were not docile laborers unwilling to fight for their rights. “They learned that the Chinese could not be taken for granted,” Stanford University’s Hilton Obenzinger told NBC News.

While Chinese workers dominated the railroad workforce in the West, most eastern and southern railroad companies relied on Black Americans to do the back-breaking construction work. Before Emancipation, companies owned, hired or rented enslaved laborers, both male and female, according to Ted Kornweibel, author of Railroads in the African American Experience. After Emancipation and the Civil War, newly freed Black Americans, looking for an alternative to dead-end sharecropping or domestic service, sought employment on the western railroad teams. Like Chinese workers, they faced sharp pay disparities and were often subject to the worst working conditions.

Once railroads became operational, they served in numerous capacities: as firemen shoveling coal into the trains’ engines, as brakemen and switchmen, baggage and freight handlers and as porters and waiters. Despite the modest pay, railroad work was seen as a steady, respectable job for newly freed Black American men, a fact noted in the blues song ‘Berta.’ “When you marry, marry a railroad man,” the lyrics instruct. “Every day Sunday, a dollar in your hand.’

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One reason it was so hard to recruit railroad labor was that the work was inherently dangerous and isolating. The landscape was rugged, the living conditions primitive and the weather often extreme. Harsh mountain winters brought the regular threat of avalanches, while brutal summer temperatures in the desert terrain could reach up to 120 degrees Fahrenheit, causing workers to collapse from dehydration and heat stroke.

One of the most hazardous areas on the route was the Sierra Nevada’s Cape Horn, a notoriously steep peak that required the railroad’s roadbed to snake around the mountain. Teams of mostly Chinese workers would be tasked with removing boulders, trees and brush from the mountain’s nearly perpendicular slope. And some would be lowered from the top of the cliff by rope or in woven reed baskets to chip away at the rock face to clear space for explosives—which they would light before signaling to be quickly pulled back up. Any imprecision or delay in pulling them up resulted in death.

While the railroads didn't keep records on workers' deaths, as many as 1,000 are believed to have died from accidental explosions and snow or rock slides, according to Stanford researchers.

To facilitate the railroad’s passage through the nation’s central and western regions, the government granted millions of acres of land to the railroad companies that actually belonged to tribal nations. Track was laid across 15 distinct tribal homelands, according to the Utah Division of State History. Not only did the construction displace Indian people from their lands, but it decimated a crucial resource: the buffalo, traditionally hunted by Plains tribes such as the Lakota, Arapaho and Cheyenne for food, shelter and trade.

According to the National Parks Service, the bison population fell from tens of millions in the early part of the 19th century to near extinction after being hunted by soldiers, railroad workers and travelers as the railroad progressed. Losing a resource so integral to their ways of life ultimately deepened Indigenous people’s dependence on the U.S. government.

Some displaced tribes resisted the occupation of their lands by raiding railroad worker camps and disrupting construction. So the U.S. government deployed the military to protect the vast public-private investment. To prevent skirmishes, railroad companies frequently called on General William Tecumseh Sherman, a celebrated Civil War leader put in charge of protecting the railroads, to send troops. Some army actions escalated into full-out attacks on native villages, such as the 1864 Sand Creek Massacre, which killed more than 200 tribal people, mostly women and children.

Not all tribes were affected the same way. Some bands of the Central Plains Pawnee nation, for example, cooperated with the U.S. government, working as scouts and helping defend railroad worksites from their historical tribal enemies.

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Efforts to depict the transcontinental railroad as a grand project created by and for white Americans began just moments after the railroad was completed in 1869, when a symbolic Golden Spike was hammered into the ground in Promontory Summit, Utah, where the rails constructed by the Central Pacific and Union Pacific met. Although the majority of railroad laborers came from China, they were left out of the formal documentation of the ceremony marking the project’s completion. The official photo shows two engineers shaking hands, surrounded by workers with champagne bottles. Not one of the workers visible in the picture was Chinese.

"History—at least photographically—says that the Chinese were not present," the late photographer Corky Lee told NPR in 2014. That erasure would continue at the transcontinental railroad’s centennial in 1969. Despite efforts by Chinese railroad workers’ descendants to seek acknowledgement of their ancestors’ labor, then-Transportation Secretary John A. Volpe failed to credit the immigrant workers in his speech, saying instead, “Who else but Americans could chisel through miles of solid granite? Who else but Americans could have laid 10 miles of track in 12 hours?”

Since then, the U.S. government and historians have worked to include the stories of the Chinese while chronicling the railroad’s creation. In 2019, in honor of the 150th anniversary of the Golden Spike ceremony, Transportation Secretary Elaine Chao paid tribute to the Chinese workers who, in her words, “risked everything to make the transcontinental railroad a reality.”