From 1922 until 1935, much of what is now US 302 was a part of the New England road marking system, designated as Route 18, from Portland, Maine, northwest to Littleton, New Hampshire, roughly . From Littleton west to Montpelier in Vermont, US 302 and Route 18 took different paths. NE-18 took a more northerly route, along present-day New Hampshire Route 18 and Vermont Route 18 to St. Johnsbury, Vermont (closely paralleling I-93), then along present-day US 2 up to Montpelier.