Iowa Code § 15.448: Referendum.

Within thirty days after the receipt of the list of owners of property and residents within the suggested historical preservation district, the authority shall fix a date not more than forty-five days from the receipt of the petition seeking a referendum on the question of establishment of a historical preservation district. The authority, after consultation with the county commissioner of elections, shall specify the polling place within the suggested district that will best serve the convenience of the voters and shall appoint three judges and two clerks of election from residents of the proposed district.