"A house divided against itself cannot stand." - Abraham Lincoln
Following the American Civil War, the locomotive of the US economy were the railroads. In just six years, The USA not only recovered from the civil war but also became the richest country in the world. How did they do that? By building railroads.
UNP was founded in 1862 after President Lincoln signed a law promoting the construction of railroads. Today, UNP is the largest railroad company in the world with a market cap of 110 Billion USD. There are four big railroads in the US: UNP, BNSF, CSX and Norfolk Southern. UNP and BNSF have a duopoly in the West while CSX and Norfolk Southern has a duopoly in the East
Picture from: http://www.khurramhashmi.org/crbasic_info/rail-links.html