From the primitive 19th century iron horse to the thundering diesels of today, railroads have played an important part in enabling, changing, and sometimes inciting warfare. This talk is an overview of how railroads served in America's wars, and how to apply this information to design and build operating model railroads. Starting with the Crimean War in 1855 and extending to current times, the talk features prototype photos, maps and plenty of examples of world class modeling. It puts special emphasis on the US military in the American Civil War, WWI, WWII and Gulf Wars.