Iowa Code § 274.14: Restoration.

When the natural obstacles by reason of which territory has been set off by the area education agency administrator from one school district and attached to another in the same or an adjoining county, as provided in section 274.13, have been removed, such territory may, upon the concurrence of the respective boards, be restored to the school district from which set off and shall be so restored by said boards upon the written application of two-thirds of the electors residing upon the territory so set off together with the concurrence of the area education agency administrator and the board of the school district from which such territory was originally set off by the said administrator.