Northwestern Conference (IHSAA) Former members Former members

| School | City | Mascot | County | Year_joined | Previous_Conference | Year_Left | Conference_Joined |
|---|---|---|---|---|---|---|---|
| Hammond | Hammond | Wildcats | 45 Lake | 1963 | Northern Indiana | 1968 | Indiana Lake Shore |
| Hammond Clark | Hammond | Pioneers | 45 Lake | 1963 | Northern Indiana | 1968 | Indiana Lake Shore |
| Hammond Tech | Hammond | Tigers | 45 Lake | 1963 | Northern Indiana | 1968 | Indiana Lake Shore |
| Valparaiso | Valparaiso | Vikings | 64 Porter | 1963 | Northern Indiana | 1968 | Independents |
| Whiting | Whiting | Oilers | 45 Lake | 1963 | Northern Indiana | 1968 | Indiana Lake Shore |
| Hammond Gavit | Hammond | Gladiators | 45 Lake | 1966 | Independents | 1968 | Indiana Lake Shore |
| Hammond Morton | Hammond | Governors | 45 Lake | 1966 | Independents | 1968 | Indiana Lake Shore |
| Hobart | Hobart | Brickies | 45 Lake | 1966 | Independents | 1968 | Independents |
| Andrean | Gary | 59ers | 45 Lake | 1968 | Independents | 1975 | Independents (school moved to Merrillville ) |
| Gary Wirt | Gary | Troopers | 45 Lake | 1970 | Calumet | 2009 | school closed |