1946-47: 11 teams

The Basketball Association of America (BAA) was founded in 1946. The new league started out with eleven franchises;

Boston Celtics
Chicago Stags
Cleveland Rebels
Detroit Falcons
New York Knicks
Philadelphia Warriors
Pittsburgh Ironmen
Providence Steamrollers
St. Louis Bombers
Toronto Huskies
Washington Capitols

Of the original eleven, only the Celtics and Knicks didn’t later fold or re-locate.

1947-48: 8 teams

The following teams folded after the ’46-47 season;

Cleveland Rebels
Detroit Falcons
Pittsburgh Ironmen
Toronto Huskies

The league brought in one new team, the Baltimore Bullets. The Washington Wizards were once known as the Baltimore Bullets, but this was a different franchise with the same name.

1948-49: 12 teams

The league added four new teams;

Fort Wayne Pistons
Indianapolis Jets
Minneapolis Lakers
Rochester Royals

1949-50: 17 teams

Before this season, the BAA merged with the NBL (National Basketball League) to from the NBA, and seven new teams joined the leauge;

Anderson Packers
Denver Nuggets (different from the current Nuggets)
Indianapolis Olympians
Sheboygan Red Skins
Syracuse Nationals
Tri-Cities Blackhawks
Waterloo Hawks

Most of the NBL’s teams were located in relatively small Midwestern cities. Two teams also folded; the Indianapolis Jets and Providence Steamrollers.

1950-51: 11 teams

The following teams folded after the ’49-50 season;

Anderson Packers
Chicago Stags
Denver Nuggets
St. Louis Bombers
Sheboygan Red Skins
Waterloo Hawks

1951-52: 10 teams

The Washington Capitols folded.

The Tri-Cities Blackhawks left Moline, Illinois for Milwaukee and became the Milwaukee Hawks, and were the first NBA team to re-locate.

1953-54: 9 teams

The Indianapolis Olympians folded.

1954-55: 8 teams

The Baltimore Bullets folded early in the ’54-55 season. The Bullets won the 1948 BAA Championship, and are the only team that won a BAA/NBA Championship to later cease operations. They were the last NBA team to fold.

1955-56: 8 teams

The Milwaukee Hawks re-located to St. Louis.

1957-58: 8 teams

The Fort Wayne Pistons re-located to Detroit and the Rochester Royals re-located to Cincinnati.

1960-61: 8 teams

The Minneapolis Lakers re-located to Los Angeles.

1961-62: 9 teams

The Chicago Packers joined the league.

1962-63: 9 teams

The Philadelphia Warriors re-located to San Francisco and the Chicago Packers changed their name to the Zephyrs.

1963-64: 9 teams

The Chicago Zephyrs re-located to become the Baltimore Bullets and the Syracuse Nationals re-located to become the Philadelphia 76ers.

1966-67: 10 teams

The Chicago Bulls joined the league.

1967-68: 12 teams

The San Diego Rockets and Seattle SuperSonics joined the leauge.

1968-69: 14 teams

The Milwaukee Bucks and Phoenix Suns joined the league and the St. Louis Hawks re-located to Atlanta.

1970-71: 17 teams

The Buffalo Braves, Cleveland Cavaliers and Portland Trail Blazers joined the league.

1971-72: 17 teams

The San Diego Rockets re-located to Houston. The San Francisco Warriors were re-named the Golden State Warriors, although this could also be considered a re-location as they moved across the bay from San Francisco to Oakland.

1972-73: 17 teams

The Cincinnati Royals re-located to become the Kansas City–Omaha Kings.

1973-74: 17 teams

The Baltimore Bullets re-located to suburban Washington, DC and were re-named the Capital Bullets.

1974-75: 18 teams

The New Orleans Jazz joined the league and the Capital Bullets were re-named the Washington Bullets.

1975-76: 18 teams

The Kansas City-Omaha Kings became the Kansas City Kings.

1976-77: 22 teams

This was the year the NBA merged with the ABA (American Basketball Association) and four new teams joined the league;

Denver Nuggets
Indiana Pacers
New York Nets
San Antonio Spurs

1977-78: 22 teams

The New York Nets re-located to New Jersey.

1978-79: 22 teams

The Buffalo Braves re-located to become the San Diego Clippers.

1979-80: 22 teams

The New Orleans Jazz re-located to Utah.

1980-81: 23 teams

The Dallas Mavericks joined the league.

1984-85: 23 teams

The San Diego Clippers re-located to Los Angeles.

1985-86: 23 teams

The Kansas City Kings re-located to Sacramento.

1988-89: 25 teams

The Charlotte Hornets and Miami Heat joined the league.

1989-90: 27 teams

The Minnesota Timberwolves and Orlando Magic joined the leauge.

1995-96: 29 teams

The Toronto Raptors and Vancouver Grizzlies joined the league, expanding the NBA into Canada for the first time since 1947, when it was still the BAA.

1997-98: 29 teams

The Washington Bullets were re-named the Wizards.

2001-02: 29 teams

The Vancouver Grizzlies re-located to Memphis.

2002-03: 29 teams

The Charlotte Hornets re-located to New Orleans.

2004-05: 30 teams

The Charlotte Bobcats joined the league.

2008-09: 30 teams

The Seattle SuperSonics re-located to become the Oklahoma City Thunder.

2012-13: 30 teams

The New Jersey Nets re-located to Brooklyn.

2013: 30 teams

The New Orleans Hornets were re-named the Pelicans.

2014-15: 30 teams

The Charlotte Bobcats were re-named the Hornets. All records of the original Charlotte Hornets (1988-2002) were transferred to the new Hornets, and the Bobcats and current Hornets are considered a continuation of the original Hornets. The history of the Pelicans now officially begins with the re-location of the original Hornets to New Orleans in 2002.