The Basketball Association of America (BAA) started the first basketball season in 1946. In 1949, the BAA agreed to merge with the National Basketball League to become the National Basketball Association (NBA). At the start, there were seventeen franchises in the nation. However, in 1950 the franchises were consolidated to eleven. In 1950, the NBA became integrated, accepting the first African American players. Chuck Cooper joined the Boston Celtics, Nat "Sweetwater" Clifton joined the New York Knicks and Earl Lloyd joined the Washington Capitols. The Minneapolis Lakers won the first NBA Championship in 1950.

The NBA was at its smallest in 1954 when it had only eight franchises, all eight of which remain today. These are the Knickerbockers, Celtics, Warriors, Lakers, Royals/Kings, Pistons, Hawks and Nationals/76ers. 1954 also saw the introduction of the 24-second shot clock to increase the tension of the game.

The NBA played with the six-team format until 1967 when it expanded by adding two teams. This expansion was in response to the founding of the American Basketball Association (ABA) in an attempt to tie up the best cities. The following year the Division Semifinals was changed to a best-of-seven playoff. Two additional teams were added each in 1975 and 1977. In 1976, the NBA reached a settlement with the ABA, which added four ABA franchises to the NBA, raising the total to 22.

The current sixteen-team tournament was not started until 1984. The First round was then changed to a best-of-five playoff, to accommodate the new teams. It wasn't until 2003 that first round became the best of seven we have today. During the last 2004 to 2005 season, the NBA underwent additional changes. There are now thirty NBA franchises and the division structure has been realigned. There are now three divisions with five teams each.