- Sabula
- Sac City
- Sageville
- Saint Ansgar
- Saint Anthony
- Saint Benedict
- Saint Charles
- Saint Donatus
- Saint Joseph
- Saint Lucas
- Saint Marys
- Saint Olaf
- Saint Paul
- Salem
- Salix
- Sanborn
- Sandyville
- Saylorville
- Scarville
- Schaller
- Schleswig
- Scranton
- Searsboro
- Sergeant Bluff
- Seven Oaks
- Sexton
- Seymour
- Shambaugh
- Shannon City
- Sharpsburg
- Sheffield
- Shelby
- Sheldahl
- Sheldon
- Shell Rock
- Shellsburg
- Shenandoah
- Sherrill
- Shueyville
- Sibley
- Sidney
- Sigourney
- Silver City
- Sioux Center
- Sioux City
- Sioux Rapids
- Slater
- Sloan
- Smithland
- Soldier
- Solon
- Somers
- South Amana
- South English
- Spencer
- Spillville
- Spirit Lake
- Spragueville
- Spring Hill
- Springbrook
- Springville
- Stacyville
- Stanhope
- Stanley
- Stanton
- Stanwood
- State Center
- Steamboat Rock
- Stockport
- Stockton
- Stone City
- Storm Lake
- Story City
- Stout
- Stratford
- Strawberry Point
- Struble
- Stuart
- Sully
- Sumner
- Sundown Mountain
- Superior
- Sutherland
- Swaledale
- Swan
- Swea City
- Swisher
