Iowa Code § 368.8
Any territory may be severed upon the unanimous consent of all owners of the territory and approval by resolution of the council of the city in which the territory is located. The council shall provide in the resolution for the equitable distribution of assets and equitable distribution and assumption of liabilities of the territory as between the city and the severed territory. The city clerk shall file a copy of the resolution, map, and a legal description of the territory involved with the county board of supervisors, secretary of state, and state department of transportation. The city clerk shall also record a copy of the map and resolution with the county recorder. The secretary of state shall not accept and acknowledge a copy of a map and resolution of severance which would create an island. The severance is completed upon acknowledgment by the secretary of state that the secretary of state has received the map and resolution.
Iowa Code § 368.8