From what country did most of the workers who built the Transcontinental Railroad come?
They came from China to build the Central Pacific Railway,
They came mainly from Ireland to build Railroad from the East.
After the Civil War, China supplied the USA a labor force to build its railroads.
About 80% of the Workforce on the Central Pacific Railway was Chinese by 1869. They hired there first Chinese workers in 1865. This was only on the Western portion of the Railway line the Eastern Railway portion was being built using European heritage workers , mainly Irish who had been displaced by the Irish potato famine. and other railway companies. The two railroads meet in Utah and a golden spike placed at the junction.
The western portion was of course more difficult and dangerous.
The granite rocks of the Sierra Nevada's had to be dynamited out.
The Eastern portion suffered from Indian attacks, and the vast distances of the American prairies. The Western portion also had to cross the Rocky mountains.
The transcontinental line did not get Congressional support until the Republican controlled Congress during the Civil War supported the idea.
The Chinese workers tended to be cheaper, sober, and more co-operative than other workers.