For those who really want to understand how the Central Pac. and Union Pac. got built in the 1860's, I know of nothing that comes close to "Empire Express" by David Haward Bain. It shouldn't be your 1st book on the topic -- it's not for everybody -- but if you really want to understand, or if you want the most authoritative source, this is your book. I especially appreciated the story of nitroglycerin -- it's something that doesn't show up in earlier books b/c the Big 4 didn't want to talk about it; but it was a key development in technology. Signor's book on Donner Pass is great for the story *after* the line opened -- operations, upgrades, etc.