523
- 52301 Marengo
- 52302 Marion
- 52305 Martelle
- 52306 Mechanicsville
- 52307 Middle Amana
- 52308 Millersburg
- 52309 Monmouth
- 52310 Monticello
- 52312 Morley
- 52313 Mount Auburn
- 52314 Mount Vernon
- 52315 Newhall
- 52316 North English
- 52317 North Liberty
- 52318 Norway
- 52320 Olin
- 52321 Onslow
- 52322 Oxford
- 52323 Oxford Junction
- 52324 Palo
- 52325 Parnell
- 52326 Quasqueton
- 52327 Riverside
- 52328 Robins
- 52329 Rowley
- 52330 Ryan
- 52332 Shellsburg
- 52333 Solon
- 52334 South Amana
- 52335 South English
- 52336 Springville
- 52337 Stanwood
- 52338 Swisher
- 52339 Tama
- 52340 Tiffin
- 52341 Toddville
- 52342 Toledo
- 52345 Urbana
- 52346 Van Horne
- 52347 Victor
- 52348 Vining
- 52349 Vinton
- 52351 Walford
- 52352 Walker
- 52353 Washington
- 52354 Watkins
- 52355 Webster
- 52356 Wellman
- 52358 West Branch
- 52359 West Chester
- 52361 Williamsburg
- 52362 Wyoming