520
- 52001 Dubuque
- 52002 Dubuque
- 52003 Dubuque
- 52030 Andrew
- 52031 Bellevue
- 52032 Bernard
- 52033 Cascade
- 52035 Colesburg
- 52037 Delmar
- 52038 Dundee
- 52039 Durango
- 52040 Dyersville
- 52041 Earlville
- 52042 Edgewood
- 52043 Elkader
- 52044 Elkport
- 52045 Epworth
- 52046 Farley
- 52047 Farmersburg
- 52048 Garber
- 52049 Garnavillo
- 52050 Greeley
- 52052 Guttenberg
- 52053 Holy Cross
- 52054 La Motte
- 52057 Manchester
- 52060 Maquoketa
- 52064 Miles
- 52065 New Vienna
- 52066 North Buena Vista
- 52068 Peosta
- 52069 Preston
- 52070 Sabula
- 52072 Saint Olaf
- 52073 Sherrill
- 52074 Spragueville
- 52076 Strawberry Point
- 52077 Volga
- 52078 Worthington
- 52079 Zwingle