The transcontinental railroad would not have been possible without constant presidential oversight british loans funding the track a large supply of immigrant labor (irish and german laborers from the east, and primarily chinese from the west) strong leadership from the owners of the central pacific railroad

The correct answer is: a large supply of immigrant labor.

The hard work of the Chinese was crucial in the construction of the railroad, being responsible for 15 tunnels along it.

An Irish foreman would usually be in charge of a tunnel together with about 40 Chinese men. About 15 men worked on the heading and the rest on the bottom of the tunnels.

the end of the gilded age coincided with the panic of 1893, a deep depression, which lasted until 1897 and marked a major political realignment in the election of 1896. this productive but divisive era was followed by the progressive era.