The history of 25Hz in Northeastern US industrial districts is oft discussed, but there was another “standard” frequency in another US region. Until 1936, what is now Los Angeles Department of Water and Power operated at 50 Hz. There is an account in the IEEE Power Engineering Review about the change intricacies for AC-powered clocks in the area. At that point frequency went up to 60Hz, but even today the area uses the classically "Euro" voltages of 220-, 110- and 33kV in their system.
Crookshank & Kinsler, 1936 Los Angeles Synchronous Clock Project June 1997 IEEE-PER
