70 ILCS 200/2-85

Members of the Board shall hold office until their respective successors have been appointed and qualified. Any member may resign from office; the resignation takes effect when the member's successor has been appointed and has qualified. In case of failure to qualify within the time required, abandonment of office, death, conviction of a felony or removal from office, a member's office shall become vacant. Each vacancy shall be filled for the unexpired term by appointment in like manner as in the case of expiration of the term of a member of the Board.