Final answer:
The United States government facilitated the building of the first transcontinental railroad by granting land and paying incentives to the railroad companies. They also passed legislation to increase the supply of immigrant labor.
Step-by-step explanation:
The United States government helped facilitate the building of the first transcontinental railroad by granting land and paying incentives to the two companies building the railroad. Congress recognized that its land reserves were the only resource the federal government controlled that could be used to finance the completion of such a project. By granting land to the railroad companies, the government increased the commercial value of the surrounding lands and stimulated land sales, resulting in greater revenue for the government.
Additionally, the government passed legislation that was favorable to increasing the supply of immigrant labor. This allowed the railroad companies to have access to a larger workforce to help with the construction of the railroad.