Despite the Civil War, California grew by 47 percent between 1860 and 1870 without the railroad. It grew by 54 percent between 1870 and 1880 with the railroad, reaching 864,694 people. It had grown more slowly and was smaller than Kansas. Calculated from Historical Census Browser.
Historical Census Browser, Univ. of Virginia Library.
Orsi, Sunset Limited, 130, 193-204, 323-29.
As I have argued above, the Central Pacific and the Union Pacific both could make money as regional roads serving San Francisco and Omaha, and through connections Chicago, respectively, but as the subsidies they paid show, they could not make money as a transcontinental. In any case, given the corruption of the books, it is very hard to make any definitive case about either road.
In the case of the Central Pacific, Mercer treated the road as a whole. He does not disaggregate the California portion of the road, which did not need subsidies to be built, from the transcontinental part of the roadNevada and Utah which probably could not have supported itself.
Mercer, Railroads and Land Grant Policy, 99-122.