At the end of the 1950s, General Electric was still new to the diesel-electric road switcher market and was trying to win market share from market leader EMD. When GE introduced the U25B, EMD felt compelled to develop a comparable locomotive. The U25B delivered 2,500 hp, while EMD's four-axle models delivered a maximum of 2,000 hp. In addition, the GE locomotive had a sophisticated system for supplying fresh air for cooling various assemblies, which at the same time kept dirt and dust away, but still made maintenance easy. Therefore the GP30 was developed while the GP20 had just appeared on the market. The type designations, which indicate the power in hp x 100, had only recently been introduced, they now deviated from them again.

The problem with fresh air was solved by redesigning the airflow, which gave the GP30 a distinctive crest. This ran from above the driver's cab to the fan housing of the optionally available dynamic brake. With the GP20, EMD encountered the problem of being able to convert a maximum of 2,000 hp with four traction motors. With minor adjustments, it was finally possible to get another 250 hp out. Although not quite at the level of the U25B, it was hoped that railroads that had been using EMD locos for a decade or two would buy this locomotive. This recipe worked because, despite the shorter production time, 948 units could be sold, while the competing model was only built 478 times. Union Pacific was the only company to buy 40 B units, some of which were equipped with steam generators for use in front of passenger trains. Over time, many GP30s have been rebuilt to extend their life. Some were still in use after 50 years and some have just been rebuilt, which will further extend their service life.