Iowa Code § 357B.2
A benefited fire district shall be governed by a board of trustees consisting of three members who shall serve overlapping, three-year terms. Each trustee shall give bond in an amount to be determined by the board of supervisors, the premium for which shall be paid by the district of the trustee. The members of the board of trustees shall be appointed by the board of supervisors from among the registered voters of the district. Any vacancy on the board shall be filled by appointment by the board of supervisors for the unexpired term. If a benefited fire district is located in more than one county, joint action of the boards of supervisors of the affected counties is required to appoint the members of the board of trustees, to determine the amount of bond, or to dissolve the district as provided in this chapter.
Iowa Code § 357B.2
98 Acts, ch 1123, §13