The 1989 World Series was played between the Oakland Athletics and the San Francisco Giants. The Series ran from October 14 through October 28, with the A's sweeping the Giants in four games. It was the first World Series sweep since 1976. The four game sweep by the Athletics at the time would mark only the third time in World Series history that a team never trailed in any game (1963, 1966, and 2004 World Series being the only other times this occurred), and the first in the playoff era (post-1968). Until 2015, this was the last time a team would win the World Series after losing in the previous year.

This marked the fourth World Series matchup, and first since 1913, between the two franchises. The previous three matchups occurred when the Giants were in New York and the Athletics resided in Philadelphia. The then New York Giants defeated the Philadelphia Athletics in the 1905 World Series four games to one, the Athletics defeating the Giants in the 1911 World Series four games to two, and then again in the 1913 Fall Classic four games to one.

Fay Vincent, who had just taken over as Commissioner of Baseball after the sudden death of his predecessor Bart Giamatti in September, presided over his first World Series and dedicated it to his predecessor's memory.

This Series was also known as the "Bay Bridge Series," "BART Series," "Battle of the Bay," and "Earthquake Series" as the two participant cities lie on opposite sides of San Francisco Bay, connected by the San Francisco–Oakland Bay Bridge and the Bay Area Rapid Transit (BART) system, and the earthquake that occurred before the start of Game 3. It was the first cross-town World Series (involving two teams from the same metropolitan area) since 1956, and only the third such series that did not involve New York City (the 1906 and 1944 World Series, which featured matchups between Chicago and St. Louis teams, were the others).

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