In 1984, each league had two divisions, East and West. The divisional winners met in a best-of-5 series to advance to the World Series, in a "2–3" format, first two games were played at the home of the team who did not have home field advantage. Then the last three games were played at the home of the team, with home field advantage. Thus the first two games were played at Wrigley Field and the next three at the home of their opponents, San Diego. A common and unfounded myth is that since Wrigley Field did not have lights at that time the National League decided to give the home field advantage to the winner of the NL West. In fact, home field advantage had rotated between the winners of the East and West since 1969 when the league expanded. In even numbered years, the NL West had home field advantage. In odd numbered years, the NL East had home field advantage. Since the NL East winners had had home field advantage in 1983, the NL West winners were entitled to it.

In what year did the league have two divisions?