Early years and slow growth
The NCAA Division I Men's Basketball Tournament started in 1939 with only 8 teams competing. For many years, the tournament grew very slowly. By 1951, there were still only 16 teams. The tournament remained small because fewer colleges played basketball at high levels, and travel and scheduling were more difficult.
The 1985 major expansion
The biggest change happened in 1985 when the tournament expanded from 53 teams to 64 teams. This was a huge jump that almost doubled the number of teams. This expansion made the tournament much more popular because more schools got a chance to compete, and fans from more regions could watch their teams play.
Growth through the 1990s and 2000s
After 1985, the tournament continued to grow slowly and steadily. More teams were added throughout the 1990s and 2000s as college basketball became more popular nationwide. Television coverage improved, and more people wanted to watch the games. By 2001, the tournament had reached 65 teams.
The 2011 First Four expansion
In 2011, the NCAA added the First Four play-in games, bringing the total to 68 teams. This meant four additional teams got to play extra games to earn spots in the main tournament bracket. The First Four games are played before the main tournament and feature the lowest-ranked teams that qualified.
Reasons for expansion
The tournament expanded for several reasons. More college basketball programs wanted to participate and compete for a national title. Fans and schools pushed for inclusion. Television networks wanted more games to broadcast because March Madness became very popular and profitable. Expanding the tournament also gave smaller colleges and universities a chance to compete on a national stage. 
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