Route 109 is a state highway in western Connecticut, running from New Milford to Thomaston.

In Morris, Route 109 heads east, then northeast and southeast, before cutting across a corner of Litchfield by the Wigwam Reservoir into Thomaston.

[1][3] In 1922, the Bantam to Morris route was designated as State Highway 310.

This became part of Route 109 when it was commissioned in 1932, running from the Bantam section of Litchfield past Bantam Lake to its current eastern terminus in Thomaston.

In 1968, the section near the Branch River in Thomaston was rerouted uphill to accommodate a flood control project.