Interstate 89 connects smaller cities and rural areas within New Hampshire and Vermont, and maintains two lanes of traffic in each direction throughout the route. Unlike its neighboring Interstates (91 and 93), it does not intersect any even-numbered Interstates along its route. It does, however, parallel (and interchange multiple times with) portions of three U.S. routes: U.S. Route 4 from Enfield to White River Junction; U.S. Route 2 from Montpelier to Colchester, and U.S. Route 7 from Burlington to the Canadian border.
Bolded cities are officially-designated control cities for signs
Starting at an intersection with Interstate 93 and New Hampshire Route 3A in the town of Bow, just south of the New Hampshire capital city of Concord, the highway runs a northwest path through the Dartmouth-Lake Sunapee Region. One exit directly serves Concord (Exit 2) before the highway enters the neighboring town of Hopkinton. East-west New Hampshire Route 11 joins I-89 at Exit 11 and runs concurrently with it for about before departing at Exit 12. At Exit 13 in Grantham, New Hampshire Route 10 enters I-89, and the pair of highways form another concurrency, this one for about . Guide signs for exit 16 southeast of Lebanon display the name "Purmort", a made-up name taken from the name of an early settler in order to meet naming conventions for interstate exits. However, a community by that name has now taken root around the exit.
The highway continues northwest, passing through Lebanon, in which the Dartmouth-Hitchcock Medical Center is located. A few miles north of this point is Dartmouth College. U.S. Route 4 parallels I-89 through Lebanon. Exits 17-20 serve the city of Lebanon and are passed in quick succession. At Exit 19, northbound New Hampshire Route 10 separates from I-89 and joins westbound U.S. Route 4 to pass through West Lebanon. The final exit in New Hampshire is Exit 20, providing access to West Lebanon's large retail district along New Hampshire Route 12A. Just after this interchange, the highway crosses the Connecticut River and enters Vermont, where it remains for the rest of its run northwest to the Canadian border.
Crossing the Connecticut River into Vermont, I-89 continues the northwesterly direction it carried in New Hampshire. The Interstate intersects I-91 at an unnumbered interchange immediately upon entering Vermont. Shortly afterward, another interchange with U.S. 4 occurs. The highway begins to enter the scenic rolling hills of Vermont, turning almost due northward about 20 miles (32 kilometres) from the New Hampshire state line, and continues through the high country of central Vermont. The Interstate passes through the towns of Sharon, Royalton, Bethel, Randolph, Brookfield, and Williamstown before reaching the "twin cities" of Barre and Montpelier in the middle of Vermont. The interstate's highest point was said to be in the town of Brookfield, although the sign stating this was taken down in the late 1990s.
Another directional shift, again to the northwest, occurs while passing the interchange for Montpelier. For the next 40 miles (64 km), I-89's path isn't so much chosen as it is logical: paralleling the Winooski River and U.S. Route 2, the highway cuts through the section of the Appalachians known as the Green Mountains, and is surrounded by peaks of over 4,000 feet (1,219 m), such as Camel's Hump. U.S. 2 crosses the Interstate frequently, and has several interchanges with it, en route to Burlington.
Interstate 89 is unique due to one instance of its signage. Just beyond (Vermont) Exit 9 on both sides of the highway, about 10 miles (16 km) north of Montpelier, signs showing the distance to the next control cities are completely in metric. While there are many instances of signs being in both miles and kilometres, this is the only case of solely metric in the entire Interstate System. (Interstate 19 in Arizona used to be the other "only signed in metric" interstate in the U.S., but has been changed over in recent years as the last 2 km have been changed.) Speed limit signs have always been posted in mph.
After Exit 11 in Richmond, I-89 leaves the Green Mountains to enter the Champlain Valley and a notable shift in the landscape is visible. Here, just outside of Burlington, the highway turns northward once again. Also, at this turn is where the only official auxiliary highway starts, Interstate 189. A second highway, Interstate 289, was proposed as a beltway through Burlington's northeastern suburbs in the 1980s; amidst controversy, the highway has only been partially completed as Vermont Route 289, a Super two roadway. It has yet to directly meet its parent.
Passing I-189, I-89 sees the busiest freeway interchange in the entire state, Exit 14. A full cloverleaf interchange at this exit provides access to downtown Burlington, the University of Vermont, and the retail-heavy Dorset Street, via U.S. 2. Heading north from Burlington, the landscape quickly fades from suburban development into rolling hills more characteristic of northern New England, providing a vista overlooking Lake Champlain. I-89 passes through Milton, Georgia, St. Albans, Swanton, and finally the border town of Highgate Springs. The highway ends at the Canadian border in Highgate Springs. Its final exit, which northbound motorists can use to reverse direction onto I-89 south without crossing the border, is Exit 22 - the highest exit number along the route. U.S. Route 7 has its northern terminus at this interchange as well.
Although the divided highway continues about 5 miles (8 km) into Phillipsburg, Quebec as Route 133, this changes back to a two-lane road, until Autoroute 35 starts outside of St. Jean, Quebec, and continues to Montreal. The I-89 border crossing is the only instance where an Interstate entering Quebec does not become an Autoroute upon entry. However, Autoroute 35 will be extended in the next few years, creating a freeway-to-freeway connection.
|Merrimack||Bow||NH 3A||At-grade intersection.|
|Southern terminus of I-89 designation.|
I-93 to I-393/US 4 - Concord, Seacoast (north); Manchester, Boston (south)
|0.2||1||Logging Hill Road - Bow|
|Concord||2.1||2||NH 13 (Clinton Street) - Concord|
|3.8||3||Stickney Hill Road||Northbound exit, southbound entrance.|
|Hopkinton||6.6||4||NH 103 - Hopkinton||Northbound exit, southbound entrance only.|
Access to US-202/NH-9 in both directions from I-89 North.
|8.5||5||US 202/NH 9 - Henniker, Keene (north); Hopkinton (south)||Left exit northbound.|
Access to US-202/NH-9 West only from I-89 North.
Access to I-89 North only from US-202/NH-9 West.
Access to I-89 South only from US-202/NH-9 East.
|10.4||6||NH 127 - Contoocook, West Hopkinton|
|Warner||14.2||7||NH 103 - Davisville, Contoocook|
|17.4||8||NH 103 - Warner||Northbound exit, southbound entrance only.|
|20.0||9||NH 103 - Warner, Bradford|
|Sutton||27.2||10||North Road||To Sutton via NH 114.|
NH 11 East (King Hill Road) - New London
|I-89 and NH 11 form a long concurrency.|
NH 11/To NH 103A - New London, Sunapee
To NH 114 - Georges Mills, Springfield
NH 10 South - Grantham, Croydon
|Southern terminus of I-89/ NH 10 concurrency.|
|48.2||14||North Grantham||Northbound entrance, southbound exit only.|
Old Route 10.
|Grafton||Enfield||50.2||15||Smith Pond Road/Old Route 10|
|52.0||16||Eastman Hill Road - Purmort||To Whaleback Ski Area.|
US 4 To NH 4A - Enfield, Canaan
|56.2||18||NH 120 - Lebanon, Hanover||To Dartmouth College.|
|Northern terminus of I-89/ NH 10 concurrency.|
US 4/NH 10 North - Lebanon, West Lebanon
|60.3||20||NH 12A - West Lebanon, Claremont|
|Windsor||Hartford||0.6||I-91 - White River Junction (north); Brattleboro (south)|
To US 5.
Norwich: use US 5 north. North Hartland: use US 5 south.
|Hartford (Quechee)||3.9||1||US 4 - Woodstock, Rutland (north); Quechee (south)||Artery road to Quechee, Woodstock, Rutland, and Killington Ski Resort.|
VT 132 to VT 14 - Sharon, South Royalton (north)
VT 107 to VT 14 - Bethel, Royalton (north); Rutland (south)
To VT 100.
VT 66 to VT 12 - Randolph
To VT 14.
To Vermont Technical College.
VT 64 to VT 12/VT 14 - Northfield, Williamstown
|To Norwich University from points south.|
VT 63 to VT 14 - South Barre, Barre
|Western terminus of VT 63.|
VT 62 to US 302 - Berlin, Barre
|Western terminus of VT 62.|
US 2 to VT 12 - Montpelier, St. Johnsbury (south)
|Northeastern Vermont via US 2 east.|
To Norwich University from points north.
US 2 to VT 100B - Middlesex, Moretown
| parallels I-89 here.|
Access to Sugarbush Resort and Mad River Glen via VT 100B from points south.
VT 100 to US 2 - Waterbury, Stowe
|Access to Sugarbush and Mad River Glen from points north.|
Bolton Valley ski resort from points south.
To Ben & Jerry's Factory Headquarters.
US 2 to VT 117 - Richmond, Williston (north), Bolton (south)
To VT 289.
To Bolton Valley from points north.
VT 2A to US 2 - Williston, Essex Junction
|To Burlington International Airport from points south.|
I-189 to US 7 - Shelburne, Burlington (north), Middlebury (south)
|88.7||14E-W||US 2 - South Burlington, Burlington||To Burlington, Champlain College, University of Vermont.|
Access to Burlington International.
|Winooski||90.5||15||VT 15 - Essex Junction, Winooski||To Saint Michael's College.|
Northbound exit, southbound entrance only.
US 2/US 7 to VT 15 - Winooski, Colchester
|97.9||17||US 2/US 7 - Lake Champlain Islands, Milton (north); Colchester (south)|
|Franklin||Georgia||106.6||18||US 7/VT 104A - Fairfax, Georgia Center (north); Milton (south)|
|St. Albans||113.8||19||US 7/VT 36/VT 104 - St. Albans|
US 7 to VT 207 - St. Albans
|Swanton||123.4||21||US 7/VT 78 - Swanton|
US 7 south - Highgate Springs
|Northern terminus of US 7.|
Northbound: last exit before Canada.
|130.3||United States/Canada border.|
Northern terminus of I-89.
I-89 north becomes Route 133.