AL East to the AL Central (to replace Milwaukee), with the expansion Tampa Bay Devil Rays joining the AL East. Later, when the Houston Astros changed ownership prior to the 2013 season, the team moved from the NL Central to the AL West, resulting in both leagues having three divisions of five teams each and allowing all teams to have a more balanced schedule. Interleague play is now held throughout the season. In 2000, the AL and NL were dissolved as legal entities, and MLB became a single, overall league de jure, similar to the National Football League (NFL), National Basketball Association (NBA) and National Hockey League (NHL)—albeit with two components called "leagues" instead of "conferences". The same rules and regulations are used in both leagues, with one former exception: the AL operated under the designated hitter (DH) rule, while the NL did not. This difference in rules between leagues was unique to MLB, as the other major professional sports leagues in the U.S. and Canada have one set of rules for all teams. In 2020, the National League (NL) used the designated hitter (DH) rule for the first time. As part of the settlement of the 2021–22 Major League Baseball lockout, this change was made permanent thus making the rules in the two leagues identical. Teams An asterisk (*) denotes a relocation of a franchise. See respective team articles for more information. History Founding In the 1860s, aided by soldiers playing the game in camp during the Civil War, "New York"-style baseball expanded into a national game and spawned baseball's first governing body, the National Association of Base Ball Players (NABBP). The NABBP existed as an amateur league for 12 years. By 1867, more than 400 clubs were members. Most of the strongest clubs remained those based in the Northeastern United States. For professional baseball's founding year, MLB uses the year 1869—when the first professional team, the Cincinnati Red Stockings, was established. A schism developed between professional and amateur ballplayers after the founding of the Cincinnati club. The NABBP split into an amateur organization and a professional organization. The National Association of Professional Base Ball Players, often known as the National Association (NA), was formed in 1871. Its amateur counterpart disappeared after only a few years. The modern Chicago Cubs and Atlanta Braves franchises trace their histories back to the National Association of Professional Base Ball Players in the