Idaho Code § 40-1303
There shall be three (3) highway commissioners in each district. The first highway commissioners of the highway district organized under the provisions of this chapter shall be appointed by the governor. It shall be the duty of the governor, in the appointment of the original highway commissioners, where there had been in existence any highway district within the boundary of the newly created highway district, to appoint whenever practicable, existing highway commissioners as they shall qualify by residence in the subdistricts of the newly created highway district as highway district commissioners of the newly created highway district. County commissioners, city mayors and city council members shall not be eligible to hold office as highway district commissioners. A copy of the certificate of each appointment shall be filed in the office of the county recorder of each county in which the highway district is located and with the clerk of the highway district. Every highway commissioner shall take and subscribe the official oath, which oath shall be filed in the office of the highway district commissioners.
Idaho Code § 40-1303