Idaho Constitution Art. XVIII, § 3. Division of counties

No county shall be divided unless a majority of the qualified electors of the territory proposed to be cut off, voting on the proposition at a general election, shall vote in favor of such division: provided, that this section shall not apply to the creation of new counties. No person shall vote at such election who has not been ninety days a resident of the territory proposed to be annexed. When any part of a county is stricken off and attached to another county, the part stricken off shall be held to pay its ratable proportion of all then existing liabilities of the county from which it is taken.