Iowa Code § 414.2: Districts.

For any or all of the purposes of this chapter, the local legislative body, referred to as the council, may divide the city into districts, including historical preservation districts but only as provided in section 15.459, of such number, shape, and area as may be deemed best suited to carry out the purposes of this chapter; and within such districts the council may regulate and restrict the erection, construction, reconstruction, alteration, repair, or use of buildings, structures, or land. All such regulations and restrictions shall be uniform for each class or kind of buildings throughout each district, but the regulations in one district may differ from those in other districts.