The board of supervisors of any county may create a county economic development commission, as a separate agency or by designation of an existing county board, commission, department or agency, as the county economic development commission. The boards of supervisors of 2 or more contiguous counties may create a regional economic development commission. Economic development commissions created under this act shall consist of not less than 3 nor more than 35 members with such powers and duties as are herein prescribed. Membership of a regional commission shall be apportioned according to the population of the respective member counties. County economic development commissions heretofore established by county boards of supervisors are validated as commissions established under this act.