Completed 150 years ago this month, the transcontinental railroad left an indelible mark on America, fundamentally reshaping the country's economy, geography and identity. The iconic photograph "East and West Shaking Hands" may capture something of the railroad's monumentality, but it also presents a woefully inaccurate picture of who actually built the thing: Not a single one of the thousands of Chinese laborers responsible for its entire western leg appears in the frame.

In "Ghosts of Gold Mountain," Stanford historian Gordon H. Chang offers the first full-fledged account of those "nameless builders," filling an egregious gap in our public memory. The story Chang tells moves west to east, following the migrants' journey from China to San Francisco to the foothills and high peaks of the Sierras. The Railroad Chinese, as Chang calls them, often left the Pearl River Delta in search of California gold. But many instead forged lives in iron, laying rails and boring tunnels through some of America's most inhospitable terrain to join the Central Pacific line with the Union Pacific. They worked harder, faster and for less pay than white workers, surviving blizzards, avalanches, dynamite accidents, cave-ins and blistering heat to do "what was widely considered at the time to be impossible."

As a writer, Chang faced his own impossible task. To date, historians have not found a single diary or letter written by one of the Railroad Chinese. Despite this dearth, Chang's account of their experiences is authoritative and engaging. Drawing on payroll sheets, folk songs and archaeological evidence, he pieces together a vivid picture of their lives — their reasons for an 1867 strike, the tools they used, even what they ate and drank. (Their consumption of tea probably helped prevent dysentery.)

If Chang's exhaustive fact-finding sometimes saps his momentum — whether workers used baskets to descend the slope near Cape Horn, Calif., is one such digression — his methodology just as often lends the book a compelling sense of mystery. Reading Chang's analysis of period photographs, for instance, is like watching a master detective work a crime scene.

His investigations are often surprisingly moving, too. The absences in the historical record he reckons with are tragic, especially because the sacrifices and contributions of the Railroad Chinese were so enormous. As Chang notes, these workers even drilled the railway's final holes, "so that the ceremonial spikes would not be damaged when 'driven' in." If our current politics are any indication, America has yet to fully reckon with its reliance on the extraordinary labors of immigrants. Chang's book is a necessary corrective to delusions about our past, and a model for how historians might "give voice to the voiceless."

Benjamin Voigt is a poet and critic who teaches creative writing at Macalester College.

Ghosts of Gold Mountain
By: Gordon H. Chang.
Publisher: Houghton Mifflin Harcourt, 312 pages, $28.