In the 1920s, State Highway 309 followed today's Route 128 in Cornwall.
Route 309 connects central Simsbury with Stratton Brook State Park, West Simsbury, and North Canton. The portion between Route 167 and the Canton town line (also known locally as Old Farms Road, Westledge Road and North Canton Road) was under consideration as a state scenic road in 1999.
Signs on US 202 and Route 10 direct motorists along Route 167 to find Route 309.