The National Basketball Association (NBA) was established on June 6, 1946 and originally known as the Basketball Association of American (BAA). Of the original 11 franchises in that inaugural season most folded within a season or two however three are still in operation today, two in their original cities (Boston Celtics, New York Knicks) and one since relocated (Philadelphia Warriors). In 1949 the BAA merged with the National Basketball League, the names were combined to form the National Basketball Association which has operated under that name ever since.

Expansion took place for the first time after the merger in 1961 with the addition of the Chicago Packers (now the Washington Wizards), following that expansion happened often usually with a new team added every other season. In 1976 a second merger took place, this time with the American Basketball Association when four teams were brought into the NBA (Denver Nuggets, Indiana Pacers, New York Nets, and San Antonio Spurs).

The Boston Celtics have won the most NBA Championships with 17, the Minneapolis/Los Angeles Lakers franchise is second with 16.