Although Major League Baseball has a long history, most studies of attendance have focused on recent years because important explanatory data, such as ticket prices, are often missing for earlier periods. This study fills gaps in the data by analyzing individual team attendance records between 1904 and 2012. If important missing variables are determined using common factors that can influence between-team attendance, the attendance function can be estimated by a panel factor model. Our results indicate that the determinants of fans’ attendance decisions have changed over time. In earlier years (1904-1957), the home team’s win record was the only significant team characteristic influencing attendance. However, in recent years (1958-2012), outcome uncertainty, size, and quality of the stadium, and playing styles have also influenced fan attendance.