They toiled through back-breaking labor during both frigid winters and blazing summers. Hundreds died from explosions, landslides, accidents and disease. And even though they made major contributions to the construction of the Transcontinental Railroad, these 15,000 to 20,000 Chinese immigrants have been largely ignored by history.

Looking back, historians say, the Chinese, who began arriving in the United States in significant numbers during the California Gold Rush of 1848-1855, were deemed too weak for the dangerous, strenuous job of building the railroad east from California.

Hilton Obenzinger, associate director of the Chinese Railroad Workers in North America Project at Stanford University, says that Central Pacific Railroad director Charles Crocker recommended hiring Chinese workers after a job ad resulted in only a few hundred responses from white laborers.

“But Crocker’s plan hit opposition amid anti-Chinese sentiment, stemming from the California Gold Rush, that gripped the state,” Obenzinger told NBC, noting that construction superintendent James Strobridge didn’t think the immigrants were strong enough to do the job.

Nonetheless, Central Pacific Railroad was desperate, says Gordon Chang, Stanford professor of American history and author of the book, Ghosts of Gold Mountain.

“White workers, whom the company wanted, did not sign on in numbers anything close to what was needed,” he says. “Crocker’s colleagues objected at first because of prejudice but then relented as they had few other options. The idea of hiring Chinese, it appears, might have been raised first by Crocker’s Chinese manservant.”

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Chinese workers building a cut and a bank at Sailor's Spur in the Sierra foothills for the Central Pacific Railroad in California, 1866.

According to the Chinese Railroad Workers Project, Central Pacific started with a crew of 21 Chinese workers in January 1864.

“In January 1865, convinced that Chinese workers were capable, the railroad hired 50 Chinese workers and then 50 more,” the Project notes. “But the demand for labor increased, and white workers were reluctant to do such backbreaking, hazardous work.”

Leland Stanford, president of Central Pacific, former California governor and founder of Stanford University, told Congress in 1865, that the majority of the railroad labor force were Chinese. Without them,” he said, “it would be impossible to complete the western portion of this great national enterprise, within the time required by the Acts of Congress.”

More Chinese immigrants began arriving in California, and two years later, about 90 percent of the workers were Chinese.

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Chinese laborers at work on construction for the railroad built across the Sierra Nevada Mountains, circa 1870s.

“Hong Kong and China were as close in travel time as the eastern U.S.,” Chang says. “The Irish (who made up the majority of the Union Pacific workforce which was laying tracks westward from Omaha, Neb.) did not come out to California in large numbers until after the completion of the Transcontinental.”

Their job duties included everything from unskilled labor to blacksmithing, tunneling and carpentry, according to the Project, with most work done with hand tools.

Of course the large number of immigrants working for Central Pacific and their hard work didn’t mean they were well-treated or well-compensated for their efforts. According to the Project, Chinese workers hired in 1864 were paid $26 a month, working six days a week.

They eventually held an eight-day strike in June of 1867.

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Chinese camp and construction train in Nevada when building of the first transcontinental railroad was being speeded across the state by the Central Pacific. 

“Chinese received 30-50 percent lower wages than whites for the same job and they had to pay for their own food stuffs,” Chang says. “They also had the most difficult and dangerous work, including tunneling and the use of explosives. There is also evidence they faced physical abuse at times from some supervisors. They protested these and the long hours and they used their collective strength to challenge the company.”

The strike ended without pay parity after Central Pacific cut off food, transportation and supplies to the Chinese living in camps, but, Chang says, the strike was not held in vain. Working conditions improved following the strike.

“They scared the pants off the company leaders,” he says.

Despite Chinese workers' contributions to building America’s historic infrastructure project, Chang says their history is often forgotten.

“Many books on the railroad focus on the Big Four and the barons of the UP,” he says. “Workers, including the Irish, receive little attention. What is more, written history has marginalized the Chinese, as with all other minorities.”