Federal Support Changed the Stakes
Union Pacific was not operating as a completely private railroad. The Pacific Railway Act provided land and government-backed financing because Congress considered the transcontinental line important to the country.
The Wilson Committee later found that government bonds combined with Union Pacific’s first-mortgage bonds were roughly enough to cover the actual cost of construction. Public support therefore helped make the project possible while insiders on both sides of the construction contracts were positioned to benefit privately.
The Pacific Railway Act tied private railroad construction directly to federal land, bonds, and national transportation goals.
National Archives, Pacific Railway Act of 1862

Sources: Pacific Railway Act of 1862, National Archives; Wilson Report, 1873, 17; Kens.