The route heads northwest from Winthrop, passing through heavily forested areas of St. Lawrence County. As NY 420 passes out of Stockholm and into Norfolk, the forests surrounding the highway begin to taper off and give way to small pockets of residences and cultivated fields. The number of homes along the route begin to increase upon intersecting Plum Brook Road, at which point NY 420 becomes lined with residences for much of its run through north Norfolk. However, the string of homes ends near the northern town line, and the highway becomes flanked by forests once more as it curves northward and enters the town of Massena.