Amends the Southwestern Illinois Development Authority Act. Adds Monroe County to the territory of the Southwestern Illinois Development Authority. Makes conforming changes. Provides that the Chairman of the Authority shall be elected by the Board annually from the voting members (rather than elected from the members appointed by the county board chairmen). Provides that members of the Board may participate in Board meetings by teleconference or video conference. Allows the Authority to also enter into intergovernmental agreements with Bond, Clinton, and Monroe counties, in addition to other entities (currently, the only counties included are Madison and St. Clair counties). Effective July 1, 2023.