A photographer from Beijing goes on an epic journey to retrace the steps of the thousands of Chinese workers who built the First Transcontinental Railroad in the United States

When the "golden spike" was driven to join the tracks of the First Transcontinental Railroad across the United States in 1869, Chinese workers-who did much of the most dangerous and backbreaking work-were kept away from the widely publicized event.

Almost 150 years later, efforts are underway to give faces to those nameless workers who played such a key role in the completion of the railroad.

"The history of Chinese rail workers remains largely unknown to both Americans and Chinese," says Li Ju, a photographer from Beijing. "People should be reminded of the Chinese workers' contribution to the US economy."

Inspired by 19th century American photographer Alfred Hart who took images of the railroad's construction, Li has traveled the route at least once a year since 2012 to shoot the same sites as Hart.

With the help of a geographical location system, Li managed to identify all the sites captured in more than 360 photos taken by Hart in the 1860s.