Interstate 91

Interstate 91 (abbreviated I-91) is an Interstate Highway in the New England region of the United States. It provides the primary north–south thoroughfare in the western part of New England. The interstate's southern end is in New Haven, Connecticut at Interstate 95; its northern end is at Derby Line, Vermont, a village in the town of Derby, at the Canadian border, where it continues as Autoroute 55. I-91 is the longest of three Interstate highways whose entire route is located within the New England states, 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 Springfield, Massachusetts, Hartford, Connecticut, and New Haven, Connecticut, in order from north to south.

Interstate 91 is 290 miles (470 km) long and runs nearly straight north and south: 58 miles (93 km) in Connecticut; 55 miles (89 km) in Massachusetts; and 177 miles (285 km) in Vermont. (The net displacement is 259 miles (417 km), and the net direction is 9.0 degrees clockwise from north or south, i.e., northeast by north or southwest by south.) I-91 parallels U.S. Route 5 for all of its length, and many of the exits along I-91 provide direct or indirect access to the older route.

Much of the route of Interstate 91 follows the Connecticut River, running from Hartford, Connecticut northward to St. Johnsbury, Vermont.