In the 1850s, the greatest obstacle facing anyone who hoped to build a railroad to the Pacific wasn't the Sierra Nevada, nor was it the Rockies. It was sectionalism in American politics; the delicate balance between North and South in Congress. The greatest barrier to getting a transcontinental railroad built in mid-century America was, in a word, slavery.
The father of the Central Pacific, Theodore Judah, wrote in 1857 that "the proposition [to build the transcontinental railroad] carries the elements of destruction with it; it cannot be done until the route is defined; and if defined, the opposing interest is powerful enough to defeat it." At the time of Judah's writing, no one doubted the need for a railroad to the Pacific, least of all men in government. The boost in commerce alone seemed to justify the project, even before gold had been discovered in California in the late 1840s. There was also the issue of territorial integrity. Although U.S. authority ostensibly spanned all the way to the Pacific coast, the reality of the situation was somewhat different. Before the transcontinental railroad, it took months overland or by sea to reach California from the eastern U.S. To mid-century legislators, the situation no doubt seemed a little like that of imperial Britain trying to control its colonies across the Atlantic a hundred years earlier. A transcontinental railroad was undoubtedly needed, but the route that it would take was far from decided.
Efforts had been made. In 1853, Congress had ordered a survey of potential routes, and Secretary of War and future Confederate leader Jefferson Davis had sent four teams across the country to identify the best one. They didn't identify one, but instead reported that several routes seemed practical (all of which eventually became railroads). Even if a single best route had been identified, nothing would have come of it. Slave state politicians would have blocked any route that seemed to favor free states and vice versa, creating a political stalemate that lasted right up to the election of Abraham Lincoln.
Lincoln, of course, is remembered as the signer of the Emancipation Proclamation and the savior of the Union. He's less known as a great friend of the transcontinental railroad, but his role in the story is similarly important. Part of Lincoln's reputation as a lawyer rested on his early work promoting the growth of the railroads, and as chief executive, Lincoln proved to be a railroad man with a truly national vision. He supported Judah's land grant proposal (giving the railroads alternating parcels of land along the transcontinental route), and he established a universal rail size, known as standard gauge, that enabled the nation's many smaller rail networks to begin to forge a greater network that was truly national.
Lincoln's early support for the transcontinental lines was crucial, and it points to the importance politics and politicians held for the project as a whole. Just as slavery—a political issue—proved more than sufficient to hamstring the efforts of Pacific rail promoters for decades, once construction was underway, favorable legislation and support in Washington remained a decisive factor. Both the Union Pacific and the Central Pacific depended on government loans, guarantees, and funding to get underway, and they lobbied constantly to keep the good will flowing. The CP's Collis Huntington and the UP's "Doc" Durant became veritable fixtures in Washington, currying favor, greasing the wheels, and at least in Durant's case, directing large amounts of stock and money toward people with positions of influence. Whereas the dominant political wisdom of the early-nineteenth century had insisted on keeping the federal government at a distance from business and the creation of infrastructure, in the time of the transcontinental railroad, it became clear that the two spheres couldn't be completely divorced.
Much has been made of the role the transcontinental railroad played in tying the Union together by uniting the proverbial "house divided." Yet the relationship between politics and private investment on the railroads in the 1860s hints that another gap was bridged, as well: the separation of government and business that had been staunchly defended just a few decades earlier.