At a ceremony on Friday, Transportation Secretary Elaine L. Chao, the first person of Chinese descent to hold the position, paid tribute to the diverse work force. In addition to Chinese workers, there were many Irish immigrants, Civil War veterans, Mormons, African-Americans and Native Americans, Ms. Chao said.

Native American communities, of course, were also forcibly displaced by the railroad and the westward expansion it enabled. An exhibit on the Chinese workers, on view at the Smithsonian through next year, also highlights the experiences of Native Americans.

Ms. Chao said that the achievements of the Chinese workers were poignant because many did not have the opportunity to become citizens, and so little record of their existence survived.

Yet the engineering feat they undertook was “every bit as consequential as the digital revolution that binds the world” today, she said.

The renewed focus on the contributions of the Chinese workers is due in large part to Gordon H. Chang, a historian at Stanford University, who has spent decades researching the workers’ history and co-directs the Chinese Railroad Workers in North America Project.