1.NBA was founded on June 6th 1946, when it was founded, it was called BAA, that is, the National Basketball Association of America. It was established by the owners of eleven ice hockey stadiums and gymnasiums in order to prevent the gymnasiums from being idle outside ice hockey competitions.
2. 1949 BAA annexed another league (NBL) at that time and changed its name to NBA. 1949-50 season, NBA*** 17 team.
3. 1976 NBA annexed American Basketball Association (ABA), and the number of teams increased to 22. In 2004, the Bobcats joined 30 teams.
I hope it helps.