From Major League Baseball All-Star Game History by Baseball Almanac:

“…Through the years, every franchise has had its share of superstar players that stand out above the rest. They are the ones that bring the fans out to the ballpark and only one game brings them all together at once, The All-Star Game.

“The first Major League All-Star Game was played on July 6, 1933 at Comiskey Park in Chicago. It was initiated at the insistence of Arch Ward, a sports editor for the Chicago Tribune, to coincide with the celebration of Chicago's Century of Progress Exposition. For [90] years, the ‘Midsummer Classic’ has remained a fan favorite showcasing the top talent in baseball.

“All-Star teams were originally selected by the managers and the fans for the 1933 and 1934 games. From 1935 through 1946, managers selected the entire team for each league. From 1947 to 1957, fans chose the team's starters and the manager chose the pitchers and the remaining players. From 1958 through 1969, managers, players, and coaches made the All-Star Team selections. In 1970, the vote again returned to the fans for the selection of the starters for each team and remains there today.”