The preservation study committee shall consist of from 5 to 9 members who shall be residents of the county or of any incorporated municipality within it. Among the members of the study committee shall be at least one representative of the county historical museum, if any; one representative of a volunteer historical society or organization concerned with preservation in unincorporated areas in the county; one member from an existing municipal landmark or historic preservation commission, if any, in the county; and a representative of the county regional planning commission, if any. The chief executive officer of the county board shall appoint a chairman from among the members of the study committee, and shall make every reasonable effort to nominate persons with a demonstrated interest in prehistory, history, or architecture as the remaining members of the study committee. The preservation study committee shall be appointed for a reasonable period of time not to exceed one year.