- Carlye Subdivision
- Carlyle
- Carman
- Carmi
- Carol Stream
- Carpenter
- Carpentersville
- Carr Island
- Carriage Lane Estates
- Carrier Mills
- Carroll Island
- Carroll Island
- Carroll Island (historical)
- Carrollton
- Carterville
- Carthage
- Carthage Lake
- Cartter
- Cary
- Cascade
- Casey
- Caseyville
- Cash Island
- Casner
- Caspars
- Castle Fin
- Castle Junction
- Castleton
- Castor Township
- Catharine