The Union Association survived for only one season (1884), as did the Players' League (1890), an attempt to return to the National Association structure of a league controlled by the players themselves. Both leagues are considered major leagues by many baseball researchers because of the perceived high caliber of play and the number of star players featured. However, some researchers have disputed the major league status of the Union Association, pointing out that franchises came and went and contending that the St. Louis club, which was deliberately "stacked" by the league's president (who owned that club), was the only club that was anywhere close to major league caliber.
Aaron hit .314 with 27 home runs and 106 RBI, in 1955. He was named to the NL All-Star roster for the first time; it was the first of a record 21 All-Star selections and first of a record 25 All-Star Game appearances.   In 1956, Aaron hit .328 and captured the first of two NL batting titles. He was also named The Sporting News NL Player of the Year. In 1957, Aaron won his only NL MVP Award,  as he had his first brush with the triple crown.  He batted .322, placing third, and led the league in home runs and runs batted in.  On September 23, 1957, Aaron hit a two-run game-ending home run in Milwaukee, clinching the pennant for the Braves and being carried off the field by his teammates. Milwaukee went on to win the World Series against the New York Yankees , the defending champions.  Aaron did his part by hitting .393 with three homers and seven RBI. On December 15, 1957, his wife gave birth to twins.  Two days later, one of the children died.  In 1958, Aaron hit .326, with 30 home runs and 95 RBI. He led the Braves to another pennant, but this time they lost a seven-game World Series to the Yankees. Aaron finished third in the MVP race and he received his first of three Gold Glove Awards . During the next several years, Aaron had some of his best games and best seasons as a major league player. On June 21, 1959, against the San Francisco Giants , he hit three two-run home runs. It was the only time in his career that he hit three home runs in a game.