It was 1959 when EMD began introducing the first of its second-gen diesels, the turbocharged GP20. Production of this popular road switcher continued through 1962 and the GP20 was built over 200 times for numerous railroads.

The GP20 was spawned from a modification Union Pacific made to a few of its GP9s. Seeking additional power output UP added turbochargers to the GP9s, boosting their HP to 2000 from 1750. This successful experiment prompted EMD to produce the GP20 with a turbocharged version of its staple 567 prime mover.

Equipped with dynamic brakes and a low, short hood, this locomotive can still be seen in operation on several short lines in the US. The SP and WP have preserved #7207 and #2001 respectively.