- Southern Terminus:
- Main Street (CT 17/CT 66) and Marlborough Street (CT 16/CT 66) in Portland
- Northern Terminus:
- Gospel Lane (CT 17) and Glastonbury Turnpike (CT 17) in Portland
- 3.02 miles
On the east side of the Arrigoni Bridge, CT 17/CT 66 turns east from Main Street onto Marlborough Street. Main Street continues north as CT 17A for about three miles through Portland to end back at CT 17. The entire length is a two-lane undivided road. It is one of the few letter-suffixed routes in Connecticut.