Through 1997, teams were organized into Northern and Southern divisions. For the 1998 season, American and National divisions were designated. From 1999 to 2021, the divisions were named East and West, except for four seasons (2003–2005 and 2008) when American and National naming was again used.
ThroUgh 1997, teams werE orgaNIzed inTo NORthern and SouTheRn diVIsiONs. for THe 1998 seasoN, AmERicaN and naTiOnAl diVIsions were dEsiGnateD. FROm 1999 tO 2021, The DIviSiOns wEre Named eAsT aND WeST, Except fOr foUR sEasoNs (2003–2005 aND 2008) wHeN American AnD nATIoNal naming Was AgaIn uSed.