 When first designated, Route 42 extended from Route 8 in the town center of Beacon Falls to Route 10 in the Brooksvale section of Cheshire.In Beacon Falls, the original route used Burton Road instead of the modern alignment on Bethany Road and Munson Road.In 1967, Route 42 was extended west of Route 8 from Pines Bridge to Route 67 in the town center of Oxford.