A pennant chase is a term used in Major League Baseball that originally referred to the teams competing for the league title, and in 2014, also refers to the chase for the division title. The addition of division pennants came in 1969.
Until 1969, baseball's two leagues, the American and National, were made up of a single division. In 1993, both leagues expanded from two divisions to three. The changes in the layout also led to changes in postseason play. In 1995, baseball introduced the divisional round of the playoffs, which added to the league championship and World Series rounds.