Major League Baseball currently has 30 teams, divided evenly between the National League and American League, with 15 clubs in each league.
The modern 30-team structure was completed in 1998, when the Arizona Diamondbacks and Tampa Bay Devil Rays joined MLB as expansion franchises. The league later realigned into six divisions: East, Central, and West in each league. MLB's 30 clubs represent 29 U.S. cities or metropolitan areas and one Canadian city, Toronto.
The number has remained 30 since the 1998 expansion, although franchises have relocated, changed names, and shifted divisions. For example, the Montreal Expos moved to Washington, D.C., in 2005 and became the Washington Nationals. The Florida Marlins also became the Miami Marlins in 2012.
A common mix-up is counting only one league, which has 15 teams, or including former MLB franchises such as the Expos. The 30-team total refers to active clubs in both leagues combined.