The 1960s onward witnessed unprecedented technological and horsepower developments in the field of diesel-electric locomotives. Spurred by market demands, EMD and GE have developed locomotives of ever-greater speeds and tractive effort, allowing the railroads to bring resources to market more quickly and cheaply. This collection of more than 200 photos features the most significant of these high-horsepower diesels, from EMD SDs and GPs to GE Dash 9s and the “green” initiative Evolution, at work across the United States and Canada. The photography is accompanied by detailed captions discussing development, function, history, and locations depicted.