This formative period of diesel locomotive evolution is examined with the help of more than 250 modern and period photos depicting passenger, freight, and switching locomotives. Author Brian Solomon covers every prominent manufacturer of the period-including Electro Motive, Alco, Baldwin, and GE-as well as iconic models like Geeps, E and F units, PAs and FAs, sharknoses, U boats, and more. The photographs take in the grand geographic and technological breadth of North American railroading and are accompanied by detailed captions identifying the locomotives pictured and explaining their roles in this crucial era of American railroading.