Original: The Church of Satan was established at the Black House in San Francisco, California, on Walpurgisnacht, April 30, 1966, by Anton Szandor LaVey, who was the Church's High Priest until his death in 1997.
Simplified: The Church of Satan started in San Francisco, California, on Walpurgis night April 30 1966, by Anton Szandor LaVey, who was the Church's high priest until he died in 1997.