 I-91 then continues past the Derby Line-Rock Island Border Crossing, where the road's official name changes to Autoroute 55.I-91 is the longest of three Interstate highways whose entire route is located within the New England states (the other two highways being I-89 and I-93) and is also the only primary (two-digit) Interstate Highway in New England to intersect all five of the others that run through the region.The largest cities along its route are New Haven, Connecticut, Hartford, Connecticut, Springfield, Massachusetts, Northampton, Massachusetts, Greenfield, Massachusetts, Brattleboro, Vermont, White River Junction, Vermont, and St. Johnsbury, Vermont in order from south to north.