- Western Terminus:
- Essex Road (CT 153) in Westbrook
- Eastern Terminus:
- Boston Post Road (US 1) in Old Saybrook
- 1.62 miles
Spencer Plain Road is a small, short east/west route in southern Connecticut. It begins at Essex Road (CT 153) in Westbrook and runs to the west for a short distance. It then curves to the south, has an interchange with the Connecticut Turnpike (I-95), and ends at Boston Post Road (US 1) in Old Saybrook.