Today, there is a lot less that separates the American League from the National League. The teams in each league play 162 games. Each is broken into three divisions: East, Central and West. In fact, teams from each league have been squaring off against one another in interleague play since 1997. Several regions, including New York, Chicago, Los Angeles/Anaheim, and the Bay Area in California, are home to teams in both leagues.
However, there is one major difference between the two. The American League uses the designated hitter. In 1973, Major League Baseball adopted Rule 6.10, which allowed teams to designate, or choose, a player to bat in place of the pitcher -- generally considered the weakest hitter on the team. That chosen player is known as the designated hitter, or DH, for short. Today, the American league uses the DH, while the National League does not.
The use of the designated hitter has for years angered baseball purists. They want to see the pitcher bat. It was one of several rule changes Major League Baseball made over the years to increase offensive production.
The designated hitter changed the face of the game very subtly. In the beginning, older players who might have retired early, found a home in the DH slot. Even former National League players found more playing time as a DH in the American League.
Moreover, because of the DH, American League pitchers became more prone to hit a batter than their National League counterparts. That's because the American League pitcher does not have to face retaliation by the opposing pitcher. And the statistics seem to bear this theory out. According to one survey taken after the DH rule was implemented, AL batters had a 10 to 15 percent greater likelihood of being hit by a pitch than batters in the National League [source: Cooley].
After the DH rule was instituted, run production also increased in the American League. The American League scored on average, one-third more runs a game than the NL during the first 36 years of the DH rule [source: Cooley].