Interstate 91

Interstate 91 Vermont
I-91 Williams River Bridge - Rockingham, VT

As seen from parallel U.S. 5, this deck truss bridge carries Interstate 91 over the Williams River in the town of Rockingham, Vermont. 08/04/07

Overview

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.

History

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 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 VT 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

Route Information

  • North End – Derby Line, VT

  • South End – New Haven, CT

  • Branch Routes – 4

  • Total Mileage – 290.37

Mileage

Connecticut – 58.00

  • Cities – New Haven, Meriden, Hartford
  • Junctions

Massachusetts – 54.99

  • Cities – Springfield, Holyoke, Northampton, Greenfield
  • Junctions Mass Pike

Vermont – 177.38

  • Cities – Brattleboro, St. Johnsbury, Newport
  • Junctions

Source: December 31, 2018 Interstate Route Log and Finders List

I-91 Annual Average Daily Traffic (AADT)

Springfield, MA 1963
Springfield, Massachusetts – 1963.

Interstate 91 extended north 4.1 miles from the Connecticut state line to end at the South End Bridge in Springfield by 1960.4

Northeast Vermont 1978
Northeast Kingdom of Vermont – 1978 Vermont Official Highway Map.

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

I-91 North

I-91 north at Derby Line, VT

Interstate 91 navigates through an S-curve northward into Derby Line, concluding in one mile at Caswell Avenue (Exit 29). 10/08/14

I-91 north at Derby Line, VT

Interstate 91 curves northeast away from parallel U.S. 5 (Main Street) to a folded diamond interchange (Exit 29) with Caswell Avenue along the Canadian border. 10/08/14

I-91 north at Derby Line, VT

The U.S. Customs Station lines the southbound roadway ahead of the Caswell Avenue overpass. Canadian Customs follows to the immediate north. 10/08/14

I-91 north at Derby Line, VT

Exit 29 departs from the north end of Interstate 91 to Caswell Avenue west to U.S. 5 (Main Street) in Derby Line. Quebec Autoroute 55 continues the freeway north 33 miles to Sherbrooke. Connections with Quebec Autoroute 10 lead travelers west to Montreal. 10/08/14

Caswell Ave at I-91

I-91 south at Derby Line, VT

Autoroute 55 transitions into Interstate 91 south leading into the community of Derby Line, Vermont. Exit 29 loops away from the freeway to Caswell Avenue beyond the U.S. border station. Photo by Shaun Ganley (03/22/15)

Caswell Ave east at I-91 - Derby Line, VT

Caswell Avenue parallels the international border east 0.4 miles from U.S. 5 (Main Street) to a folded diamond interchange with Interstate 91. 10/08/14

Caswell Ave west at I-91 - Derby Line, VT

Caswell Avenue west at the entrance ramp for Interstate 91 south to Newport, Lyndon and St. Johnsberry. 10/08/14

Caswell Ave at I-91 - Derby Line, VT

The southbound beginning of Interstate 91 from Caswell Avenue in Derby Line. 10/08/14

South End – New Haven, Connecticut

I-91 South at I-95

I-91 south at I-95 - New Haven, CT

Interstate 91 enters Downtown New Haven alongside U.S. 5 (State Street). A trumpet interchange joins the two highways at Exit 3. From there the freeway turns southward on the final approach to I-95. Ramps for Hamilton Street (Exit 2) and Route 34 (Richard C. Lee Connector) depart in advance of the Mixmaster Interchange with the Connecticut Turnpike. 06/26/05

I-91 south at I-95 - New Haven, CT

Interstate 91 southbound ahead of the Mixmaster Interchange. Addressing traffic congestion at the exchange with I-91, ConnDOT reconstructed a 7.2-mile long section of Interstate 95 in conjunction with the building of the new Pearl Harbor Memorial Bridge. The reconfigured interchange improved movements between the two freeways. 06/26/05

I-91 south at I-95 - New Haven, CT

A single lane ramp carries motorists onto Interstate 95 northbound across the Quinnipiac River into East Haven. I-95 travels east-west along the Connecticut coastal region between Bridgeport and New London through the New Haven vicinity. Route 34 spurs west from Exit 1 into Downtown New Haven. 06/26/05

I-95 North at I-91

I-95 north at I-91 - New Haven, CT

A large diagrammatic overhead preceded the exchange with Route 34 west (Exit 47) and I-91 north (Exit 48) at the Howard Avenue overpass along Interstate 95 north. Route 34 stems west into Downtown New Haven from the Connecticut Turnpike while I-91 provides the main route to Hamden, Wallingford, Meriden and Hartford. 07/27/07

I-95 north at I-91 - New Haven, CT

A large diagrammatic overhead preceded the exchange with Route 34 west (Exit 47) and I-91 north (Exit 48) at the Howard Avenue overpass along Interstate 95 north. Route 34 stems west into Downtown New Haven from the Connecticut Turnpike while I-91 provides the main route to Hamden, Wallingford, Meriden and Hartford. 07/27/07

I-95 north at I-91 - New Haven, CT

Exit 47 to Route 34 (Richard C. Lee Connector) was also relocated from the left side of I-95 north to a new flyover separating from the right lane. Route 34 spurs west to Martin Luther King, Jr. Boulevard and Church Street in Downtown New Haven. A 24.37 mile long highway to Newtown, Route 34 was originally proposed to continue westward along a freeway to Derby Avenue and Route 122 (Forest Road) in West Haven. 07/27/07

I-95 north at I-91 - New Haven, CT

Traffic formerly separated with two lanes for I-91 and I-95 at Left Exit 48. Paralleling U.S. 5, Interstate 91 stems north from the Mixmaster Interchange with I-95 and Route 34 to the capital city of Hartford, Springfield, Massachusetts, and Brattleboro, Vermont. 07/27/07

Sources:

  1. Celebrating the 50th Anniversary of the Eisenhower Interstate Highway System: Previous Interstate Facts of the Day by the Federal Highway Administration (FHWA).
  2. Outline History of Vermont State Highways – National Highway Week, September 19-25, 1965. Prepared for informational purposes only by the Vermont Department of Highways.
  3. Vermont’s 14-Year Planning Program on the Federal Aid Highway System by the Vermont Department of Highways (April 1963).
  4. Interstate 91-Massaschusetts, BostonRoads.com.
  5. “Next up: Reconstructing the Route 34, I-91 interchange (video, animation).” New Haven Register, April 25, 2010.
  6. “New Haven Interstate 95-91 interchange to head in new direction for first time in 60 years.” New Haven Register, July 10, 2016.

Page updated January 25, 2020.