"The Schoellkopf station complex eventually met with a very unusual fate. In 1956, it was almost completely destroyed by a massive rockslide from the towering cliff above. Following this catastrophe, 11 of the generators in Station No. 3A were rebuilt for 60-Hz operation, but Stations No. 3B and 3C were completely abandoned. "
Okay, 60Hz wasn’t universally used like today. I stand corrected.