Prior to 1900, there was only the National League, and it consisted of 8 teams. Between 1876 and 1891, more than 27 teams played in the league, although the league never had more than 8 teams. In 1892, the league expanded to 12 teams with the inclusion  of 4 teams from the American Association.
** Set includes only NL teams **
*** No Top 10 Team Set is available for these seasons ***