Major League Baseball expands outside the confines of the United States as the National League announces expansion for the first time in seven years, awarding franchises to Montreal as well as San Diego, to begin play next season.

On May 27, 1968 — Major League Baseball expands outside the confines of the United States as the National League announces expansion for the first time in seven years, awarding franchises to Montreal as well as San Diego, to begin play next season.

Source:
Baseball Reference May 27