| 1891 | Basketball invented at Springfield, Mass., by James Naismith. |
| 1895 | Chicago (Austin) becomes first Illinois secondary school to organize a girls basketball team. |
| 1896 | Chicago (Austin) defeats Oak Park (O.P.-River Forest) in first known girls basketball game between Illinois high schools. |
| 1900 | Four Chicago area girls teams form first high school basketball league in Illinois. |
| 1907 | Chicago Public School Superintendent Edwin G. Cooley prevents Chicago girls teams from organizing annual basketball league. |
| 1908 | IHSAA prohibits high school girls from participating in interscholastic athletics, particularly basketball. |
| 1920 | Illinois League of High School Girls Athletic Associations (ILHSGAA) formed to promote girls athletics. |
| 1926 | ILHSGAA absorbed into IHSAA. |
| 1930 | First "telegraphic" (or "postal") basket-shooting contest sponsored by the IHSAA. |
| 1940 | IHSAA (Illinois High School Athletic Association) becomes IHSA (Illinois High School Association); private schools allowed to join IHSA. |
| 1973 | IHSA allows girls to participate in interscholastic basketball contests. |
| 1975 | Final "postal" basket-shooting contest conducted. |
| 1977 | First state girls basketball tournament held at Horton Fieldhouse on the campus of Illinois State University at Normal; Sterling defeats Washington in title game. |
| 1978 | State final tournament moved to Assembly Hall in Champaign. |
| 1979 | Sub-regional stage (for small schools only) replaced by district tournament stage. |
| 1980 | Tournament split into Class A (small schools), won by Benton, and Class AA (large schools), won by East St. Louis (Lincoln); district tournament stage eliminated. |
| 1982 | In one-year experiment, state final field reduced from eight teams to four; quarterfinal games held at four sites. |
| 1988 | First tournament played under new rule allowing three-point field goal. |
| 1990 | Teutopolis becomes first school to win three consecutive titles. |
| 1991 | Class AA teams seeded in sectional complexes instead of at the regional stage; regional games played on court of higher seed. |
| 1992 | State final tournament moved to Redbird Arena in Normal and split into two consecutive weekends, Class A and Class AA, held prior to the boys tournament. |
| 1993 | "Happening" three-point contest held for first time. |
| 2003 | Chicago Public League champion no longer given automatic berth in Class AA state finals; Public League teams enter tournament at regional level in either Class A or Class AA; Class AA teams seeded in modified sectional complex with fixed regional sites. |
| 2004 | Class A teams seeded in modified sectional complex with fixed regional sites, divided into two sub-sectionals. |
| 2005 | Some Class AA sectionals seeded in two sub-sectionals. |