By the 18th Olympiad, in 708 B.C., the Pentathlon (broad jump, discus, javelin, running, and wrestling) had been added. Originally, the only event was the race. Jason, of Argonaut fame, is credited with inventing the contest. According to legend, when Jason instituted the event, he awarded the prize to his friend Peleus.
Donald Kyle (p.122) says the first winner of three events was declared winner. He says that the broad jump, discus throw, and javelin hurl probably occurred first.