Interstate 90

Number of Miles 3112.82

• Washington - 297.52 miles
• Idaho - 73 miles
• Montana - 558 miles
• Wyoming - 207 miles
• South Dakota - 412 miles
• Minnesota - 275 miles
• Wisconsin - 188 miles
• Illinois - 103 miles
• Indiana - 157 miles
• Ohio - 244 miles
• Pennsylvania - 47 miles
• New York - 391 miles
• Massachusetts - 159 miles

Major Cities Along the Route

• Seattle, Washington
• Spokane, Washington
• Sioux Falls, South Dakota
• Madison, Wisconsin
• Chicago, Illinois
• Gary, Indiana
• Toledo, Ohio
• Cleveland, Ohio
• Erie, Pennsylvania
• Buffalo, New York
• Rochester, New York
• Syracuse, New York
• Albany, New York
• Boston, Massachusetts

Intersections with other Interstates

• Interstate 5 in Seattle, Washington
• Interstate 82 in Ellensburg, Washington
• Interstate 15 in Butte, Montana[?]. They stay merged for about 9 miles.
• Interstate 94 in Billings, Montana
• Interstate 25 in Buffalo, Wyoming
• Interstate 29 in Sioux Falls, South Dakota
• Interstate 35 in Albert Lee, Minnesota[?]
• Interstate 94 in Tomah, Wisconsin[?]. They stay joined until Madison, Wisconsin.
• Interstate 39 in Portage, Wisconsin. They stay joined until Rockford, Illinois.
• Interstate 43 in Beloit, Wisconsin
• Interstate 94 in Chicago, Illinois. They stay joined for a few miles.
• Interstate 55 in Chicago, Illinois
• Interstate 65 in Gary, Indiana
• Interstate 94 in Portage, Indiana
• Interstate 80 in Portage, Indiana. They stay merged until Clearview, Ohio[?].
• Interstate 69 in Fremont, Indiana
• Interstate 75 in Toledo, Ohio
• Interstate 71 in Cleveland, Ohio
• Interstate 77 in Cleveland, Ohio
• Interstate 79 in Erie, Pennsylvania
• The eastern Interstate 86 in Erie, Pennsylvania
• Interstate 81 in Syracuse, New York
• The eastern Interstate 88 in Schenectady, New York
• Interstate 87 in Albany, New York
• Interstate 91 in Springfield, Massachusetts
• Interstate 84 in Sturbridge, Massachusetts[?]
• Interstate 95 in Newton, Massachusetts
• Interstate 93 in Boston, Massachusetts

Spur Routes

• Rapid City, South Dakota - I-190
• Chicago, Illinois - I-190, I-290
• Cleveland, Ohio - I-490
• Buffalo, New York - I-190, I-290, I-990
• Rochester, New York - I-490, I-590
• Spur to Corning, New York[?] - I-390
• Syracuse, New York - I-690
• Utica, New York - I-790
• Schenectady, New York - I-890
• Spur to Marlborough, Massachusetts - I-290
• Spur to Leominster, Massachusetts - I-190

Notes I-90 terminated at Interstate 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 beyond the 3111.52 miles already paved.

You can't be the longest Interstate without having a few quirks. In Montana right by the Idaho border, I-90 is not a divided highway for a few stretches. The speed limit there is still "reasonable and prudent".

Not only is the I-90 section of the NYS Thruway marked backwards, with mile numbers going down as you go east, but there are two metric only signs when you drive westbound. They are around Syracuse, which is nowhere near Canada. The NYS Thruway admin decided to test metric signage (which I am told included [briefly] an 88 km/h speed limit sign) on the Thruway. Now the legend part: When one of the metric pushes was on, the state representative from that district was deadset against it. The Thruway chose his district (Liverpool, next to the former GE plant) as the test site.

If you care, I-990 is the highest number given to an Interstate.