My Tl;dr would be a little longer - early systems used both higher (around 130 hz) which caused issues with resonance and difficulties making induction motors, and lower (around 30hz) which caused light flicker.
50-60 hz solved these issues, Westinghouse thought 60hz was better for light flicker and beat out GE who settled on the 50hz standard used by it's European affiliate that moved up from 40hz due to flicker.
In Seattle you can take a tour of the Georgetown Steam Plant, which was an early power station. At one point they mention that the plant had two totally separate generators at different frequencies: one for household mains power and one for the electric streetcars.
25hz is part of the "around 30hz" I mentioned. It was a compromise for the Niagra falls turbines between 16.7hz which was good for large motors at the time and flickering lights for which Westinghouse wanted at least 33.3hz.
