During the 2014-2015 NBA season, each team in the Southwest Division (Houston, Memphis, San Antonio, Dallas, New Orleans) of the Western Conference made the playoffs.
Has this happened before? If so, in which seasons has all teams in a division made the playoffs? I recognize there was a realignment that took place for the 2004-2005 NBA season, but during the 2003-2004 NBA season, almost all teams in the Midwest division (6 of 7 teams) of the Western Conference made the playoffs.