- Western Terminus:
- Litchfield Road (US 202) in New Milford
- Eastern Terminus:
- Watertown Road (US 6) in Thomaston
CT 109 is an east/west route in Litchfield County. It begins at Litchfield Road (US 202) in New Milford and runs east while US 202 curves to the northeast. It extends to Thomaston, where it ends at Watertown Road (US 6), just west of the CT 8 expressway.