The World Series of Poker (WSOP) is a world-renowned series of poker tournaments held annually in Las Vegas. The first WSOP in 1970 was an invitational wherein Benny Binion invited six of the best known poker players to the Horseshoe Casino. At first, the WSOP grew slowly. It was twelve years before the WSOP drew 52 participants, in 1982. In the early 1980s, satellite tournaments were introduced, allowing people to win their way into the various events. By 1987, there were over 2,100 entrants in the entire series. Participation in the Main Event peaked in 2006, with 8,773 players competing.