The alternating current system we use today was the brainchild of Nikola Tesla (1846 - 1943). He was born in Croatia but moved to the United States in 1884 and initially worked for Thomas Edison, but left after Edison decided not to use AC. He sold the rights to many of his AC patents to George Westinghouse.
Tesla was a brilliant scientist and was able to show, by experiments and mathematics, that the optimum frequency for AC was 60 Hz, although he was quite a difficult person to get on with, and not everyone agreed with his ideas, and so 50 Hz, which is not quite so efficient, eventually became the standard for some countries.
