It was a seminal moment in American history: the inauguration of the first Transcontinental Railroad on May 10, 1869, in Promontory, Utah.

The day marked a profound transformation. A dangerous journey that once took months could now be completed in a week, revolutionizing the fractured country’s economy.

The leaders of the Central Pacific and Union Pacific Railroads came together to celebrate the joining of the tracks, and Leland Stanford, the business tycoon and political leader who founded Stanford University, drove a ceremonial golden spike into a tie to unite them.

But many of the workers who had built the railroad were all but invisible at the ceremony, and in its retelling for many years afterward. They included about 15,000 Chinese immigrants — up to 90 percent of the work force on the Central Pacific line — who were openly discriminated against, vilified and forgotten.

Now those workers are being written back into the history of the railroad, thanks to the dogged efforts of their descendants and of scholars. At the 150th anniversary of the golden spike ceremony on Friday, and at associated events held last week in Utah, thousands gathered to recognize a more complete picture of the monumental feat.