Interstate 91 provides a backbone route for western New England. Throughout Connecticut and a good portion of Massachusetts, I-91 serves populous areas and old industrial cities, including New Haven, Hartford and Springfield. North of there, it parallels the Connecticut River along the picturesque border of Vermont as it nears the “La Belle Province” of Québec.
High Priority Corridor
I-91 in Connecticut is part of High Priority Corridor 66: Interstate 91 Connecticut.
Parallel U.S. Routes
Interstate 91 primarily bypasses communities along U.S. 5 in Connecticut, Massachusetts and Vermont. I-91 also overlaps with U.S. 20 briefly through Springfield.
Within Massachusetts, Interstate 91 opened first from both Connecticut north to Springfield and from U.S. 5/Route 10 north of Greenfield to the Vermont state line in 1960. The 55 mile long route through the Bay State was completed in 1970.4
Interstate 91 from the Massachusetts State line north to Brattleboro in Vermont opened to traffic on November 1, 1958.1 This was the first route with controlled access completed in Vermont.
Within Vermont, Interstate 91 was built in stages in the late 1950s and through the 1960s. Specific opening dates for certain segments are as follows:2
- Guilford to Vernon (5.879 miles) – November 1, 1958
- Vernon to Brattleboro (1.942 miles) – July 31, 1959
- Brattleboro (3.918 miles) – October 5, 1960
- Brattleboro to Putney (11.055 miles) – December 6, 1961
- Putney to Westminster (2.973 miles) – August 10, 1962
- Derby (2.812 miles) – November 20, 1962
- Derby (2.106 miles) – August 21, 1963
- Westminster to Rockingham (9.437 miles) – November 7, 1963
- Rockingham to Ascutney (16.319 miles) – 1965
Near St. Johnsbury (between Wells River and Glover), two alternative alignments for Interstate 91 were submitted by the state of Vermont to the federal Bureau of Public Roads. One route stayed close to U.S. 5 through McIndoe Falls, Barnet, St. Johnsbury and Lyndonville, then shifted to Vermont Route 122 through Wheelock and Sheffield to Glover. The other alignment took an entirely different course between Wells River and Glover, offering a more direct path through Danville. The first alternative was the one ultimately built.3
Though New Haven, Interstate 95 opened to traffic as part of the Connecticut Turnpike in 1958. The route was built on landfill through Long Wharf and across the Quinnipiac River. Route 34, the Oak Street Connector, tied into the turnpike by 1960. I-91 was added to the mix when it was completed in 1966.1 The complicated exchange joining the three limited access routes was dubbed the “Mixmaster Interchange.”
Major reconstruction of the Mixmaster Interchange went to bid on April 28, 2010 as part of CTDOT’s $2 billion New Haven Harbor Crossing Corridor Improvement Program. Work involved relocating left exit ramps to Route 34 and I-91 from Interstate 95 north, eliminating a weaving traffic pattern, roadway widening and increasing the spacing between exits. Construction ran in tandem with the $433 million replacement of the Q Bridge (Pearl Harbor Memorial Bridge) along Interstate 95.5
The left side connection to Interstate 91 north from I-95 north was permanently replaced with a new right side exit on July 16, 2016. The change represented the last major traffic shift in the six-year project. Remaining work through September 2016 expanded each merge to two lanes and completed a fifth lane along I-95 north across the Pearl Harbor Memorial Bridge (scheduled for August 22). Final work on the overall interchange project wrapped up in 2017.6
Are you prepared for New Haven’s “big flip”? I-95 NB Exit 48 to I-91 NB will be on right! https://t.co/dyefDVsPgt pic.twitter.com/YNnjvXZp8J
— Q-Bridge (@QBridgeProgram) July 13, 2016
Connecticut – 58.00
Massachusetts – 54.99
Vermont – 177.38
Source: December 31, 2021 Interstate Route Log and Finders List
I-91 Annual Average Daily Traffic (AADT)
Sources: MassDOT Transportation Data Management System 2018 AADT
2018 (Route Log) AADTs State Highways (VTrans)
Interstate 91 extended north 4.1 miles from the Connecticut state line to end at the South End Bridge in Springfield by 1960.4
The final stretch of Interstate 91 opened in the Green Mountain State was located near St. Johnsbury. I-93 was completed west to I-91 in 1982.
North End – Canadian International Border – Derby Line, Vermont
South End – New Haven, Connecticut
South End Throwback
- Celebrating the 50th Anniversary of the Eisenhower Interstate Highway System: Previous Interstate Facts of the Day by the Federal Highway Administration (FHWA).
- Outline History of Vermont State Highways – National Highway Week, September 19-25, 1965. Prepared for informational purposes only by the Vermont Department of Highways.
- Vermont’s 14-Year Planning Program on the Federal Aid Highway System by the Vermont Department of Highways (April 1963).
- Interstate 91-Massaschusetts, BostonRoads.com.
- “Next up: Reconstructing the Route 34, I-91 interchange (video, animation).” New Haven Register, April 25, 2010.
- “New Haven Interstate 95-91 interchange to head in new direction for first time in 60 years.” New Haven Register, July 10, 2016.
- Pearl Harbor Memorial Bridge, Connecticut, US. Road Traffic Technology, web site.
Page updated June 7, 2022.