Interstate 90

Intersections with other Interstates

Spur Routes

Unusual Hazards

Notes

From the Wisconsin/Illinois border east, the majority of I-90 is tolled, along the following toll roads:

Almost all of the New York portion of the road is a toll road, the major east-west portion of the New York State Thruway, operated by the New York State Thruway Authority. It was originally constructed as part of the Thruway project in the middle 1950s and received its current designation as Interstate 90 in 1958. The Massachusetts stretch, also a toll road built in the mid-1950s, is known as the Massachusetts Turnpike.

I-90 incorporates two of the longest floating bridges in the world, the Lacey V. Murrow Memorial Bridge and the Homer M. Hadley Memorial Bridge, which cross Lake Washington from Seattle to Bellevue via Mercer Island, Washington. They are the second and fifth longest such bridges, respectively.

I-90 terminated at I-93 in Boston until it was connected through to the Ted Williams Tunnel in January 2003 as part of the Big Dig, extending I-90 to Boston's Logan International Airport, an additional 1.3 miles (2 km).

Until 1995 in Montana right by the Idaho border, I-90 was not a divided highway for a few stretches, having only a narrow paved median. Until 1999, the speed limit in Montana was "reasonable and prudent"; it is now 75 mph (121 km/h).

Not only is the I-90 section of the New York State Thruway marked backwards, with mileposts and exit numbers going down as one goes east, but there used to be two metric-only signs going westbound. They were around Syracuse, which is about 100 miles (161 km) from Canada. The NYS Thruway administration decided to test metric signage, which may have included (briefly) an 88 km/h speed limit sign, on the Thruway. There was also a sign displaying the distance to the Interstate 81 interchange in kilometers in Dewitt.

I-990 is the highest number given to an Interstate.

To add to the quirks about the longest interstate, it also has the longest distance twinned with another interstate (I-80 in Ohio and Indiana, I-94 in Illinois and Wisconsin) in the most states (Ohio, Indiana, Illinois, and Wisconsin). It also intersects the same interstate six times (I-94 near Michigan City, Chicago (southside), Chicago (northside), Madison WI, Tomah WI, and Billings MT).

Technically I-90 is not a complete Interstate, as the Chicago Skyway is signed as "TO I-90"; see List of gaps in Interstate Highways for more information. This makes I-80 the longest Interstate without any gaps between the endpoints.

Between LaPorte, Indiana and Toledo, Ohio, with Interstate 80, it is nowhere more than 10 miles (16 km) from the Michigan state line.