While it's impossible to take a transcontinental ride across the United States on the Union Pacific (the railroad doesn't exist anymore), visitors can get a sense of what such a ride would have been like via this fine set of digital exhibits. The Central Pacific Railroad Museum has been online since 1999, and it has grown from a few modest galleries of photographs to include thousands of stereoviews, photographs, engravings, maps, and ephemera. The different sections of the site include "steam locomotives", "Sierra Grade Construction Views", and "railroad maps". The materials on the site are a bit difficult to search, so it can be a challenge to find material quickly. Visitors shouldn't miss Nelson's 1871 Central Pacific Railroad (CPRR) guidebook, which contains a set of lovely renderings of the way west along the rails. The site is rounded out by a FAQ section.