The highest attendance for Major League Baseball (USA)during a single-season is 73,070,631 in 2005; an average of 30,936 per game.
The previous record was for the 2004 season, with 73,022,969 (or an average of 30,401 per game). NB 2005 figures released in September - four days before the end of the 'regular' season. Source: MLB sets single-season attendance record Baseball in 'golden era,' breaks mark for second straight season http://g.msn.com/0MN2ET7/2?http://www.msnbc.msn.com/id/9542489/from/ET/&&CM=EmailThis&CE=1
Comments below may relate to previous holders of this record.