Lot's of name have already been mentioned. I've got one rather unknown: Jonas Wenström who invented (and patented) the 3-phase generator in 1889. (Tesla came up with the concept of polyphase at the same time, but the Wenström patent was a full working system.)

And to you who thinks grounding is a modern thing: The first Wenström generator in 1882 refused to work since it had one ground wire to many. Once it was cut, the generator worked. [Linked Image]