Idaho Code § 50-404: Registration of electors.

All electors must register before being able to vote at any municipal election. The county clerk shall be the registrar for all city elections and shall conduct voter registration for each city pursuant to the provisions of chapter 4, title 34, Idaho Code. To be eligible to register to vote in city elections, a person shall be at least eighteen (18) years of age, a citizen of the United States and a resident of the city for at least thirty (30) days next preceding the election at which he desires to vote, or a resident of an area annexed by a city pursuant to the provisions of chapter 2, title 50, Idaho Code.