Some major events in the history of baseball include the first World Series, Jackie Robinson's debut, Babe Ruth's trade to the Yankees and Hank Aaron's record home run. Other important events in baseball history were Bill Mazeroski's walk-off home run in the 1960 World Series, Joe DiMaggio's 56-game hitting streak in 1941 and the introduction of free agency in the 1970s.
The Boston Americans defeated the Pittsburgh Pirates in the first World Series in 1903. This was possible following the agreement between the National League and the American League that continues to this day. Because of the elevated importance of these leagues, independent leagues eventually joined the two major leagues.
The Boston Red Sox traded pitcher Babe Ruth to the New York Yankees in 1920. Although Ruth was known as a star pitcher with the Red Sox, he was developing home run ability when the Yankees acquired him. With the Yankees, Ruth hit the majority of his 714 home runs and led the team to four World Series titles. This lopsided trade also ignited the eventual rivalry between the Red Sox and the Yankees.
Jackie Robinson played his first game with the Brooklyn Dodgers in 1947. This was notable because Major League Baseball had not openly accepted a black player for 50 years. Also, the 1940s still saw segregation in many aspects of life; the civil rights movement would not take hold for almost another decade after Robinson's arrival. Robinson, a Hall of Fame player, opened the door for other black players to play in the major leagues.
Hank Aaron hit his 715th home run in 1974. Babe Ruth's home run record of 714 was considered unbreakable, which made Aaron's accomplishment surprising. Aaron was also the first black player to hold the home run record.