The GG1 of the Pennsylvania Railroad is most likely the most iconic American electric locomotive of all times. It was conceived in the thirties as a more powerful and faster successor to the 2-C-2 class P5. It got a 2-C+C-2 wheel arrangement and won in trials against the 2-D-2 prototype of class R1 since this had a too long rigid wheelbase. Since the 4-6-0 wheel arrangement led to the class prefix G in the PRR, the new locomotive was called GG1 due to its wheel arrangement basically resembling two 4-6-0 locomotives which are coupled together back to back. Its streamlined Art Deco body was drawn by Donald Roscoe Dohner, but finished by Raymond Loewy.

The main frame of the GG1 consisted of two parts which were joined by a ball joint. Each half consisted of a four-wheel leading bogie and six powered wheels. Each axle had two 385 hp traction motors which were joined together and transmitted their power through a quill drive. The body of the locomotive was one-part and housed the transformer and the oil-fired steam heating boiler in the middle. The two cabs where also placed in the middle section to increase safety in collisions. The hoods on both ends only housed auxiliary equipment and carried the pantographs.

After the prototype was completed in 1934, 57 more were built by General Electric and the PRR's Altoona works. Some of these got components from Westinghouse and Baldwin. Another batch of 81 locomotives was built at Altoona between 1937 and 1943. Although designed for a speed of 100 mph or 161 km/h, the most time of their lives they only operated at scheduled speeds of 75 to 80 mph. 

In the fifties, when the need for passenger locomotives dropped, the first 57 locomotives were re-geared for a top speed of 90 mph and used in freight service. When the PRR and NYC were merged into the Penn Central in 1968, 119 were still operating. After the Penn Central's bankruptcy, Amtrak bought 30 and leased 21 more. After these had been replaced by the AEM-7, they were retired in 1980. The last operator of the GG1 was New Jersey Transit who retired them in 1983. Today, the prototype and 15 more are being preserved in museums.