Interstate 90 is the longest interstate highway in the U.S. stretching 3112 miles from Seattle, WA to Boston, MA. Driving east on I-90 from Seattle you pass through the states of Washington, Idaho, Montana, Wyoming, South Dakota, Minnesota, Wisconsin, Illinois, Indiana, Ohio, Pennsylvania, New York and Massachusetts. It is the northernmost east-west interstate except for an 1100 mile stretch of Interstate 94 passing through Montana, North Dakota, Minnesota and Wisconsin. I-94 is also farther north in Michigan as well as I-96, also in Michigan. Most of I-90's exit numbers use the mileage based system with the exception of New York and Massachusetts.

Washington

Idaho

    I-90 in Idaho is 73 miles long from the Washington border to the Montana border. The route passes through Coeur d'Alene, the 4th of July Pass, and Kellogg before passing over Wallace on a viaduct on the edge of town. The only stop light on I-90 from Seattle to Boston was in Wallace, Idaho until the early 1990s when the overhead bridge was built. In the eastern panhandle of Idaho I-90 climbs a steep and winding path to Lookout Pass where it crosses into Montana. The speed limit is 50 MPH there. Not many trucks are seen on this section which traverses the Rocky Mountains.

Montana

Wyoming

    I-90 in Wyoming is 207 miles long passing through the northeast corner of the state from the Montana border to the South Dakota border. There are lots of snow fences up along the interstate in the high plains of Wyoming. The route passes Sheridan, Buffalo, and Gillette before crossing into South Dakota.

South Dakota

    I-90 in South Dakota is 412 miles long from the Wyoming border to the Minnesota border. The exit that was Exit 66 was relocated to Exit 67 to improve access to Elmsworth Air Force Base in an effort to keep the base open. I-90 crosses the Missouri River about mid-way through the state in Chamberlain.

Minnesota

    I-90 in Minnesota is 275 miles long from the South Dakota border to the Wisconsin Border. The first segment completed was a by-pass around Austin in 1960. I-90 in Minnesota, which follows what used to be US Highway 16 was completed in 1980. It runs parallel and about 10 miles north of the southern border through the tall grasses of the high plains in the Western Great Lakes Lowland region. Most of the cross country traffic takes I-90 in Minnesota as opposed to I-94 to the north.

Wisconsin

    I-90 in Wisconsin is 188 miles long from the western border of Minnesota at the Mississippi River to the Illinois border. I-90 merges with I-94 in Tomah with both routes sharing the same interstate highway for 95 miles across the middle of the state to Madison, Wisconsin. The first stretch of I-90 in Wisconsin started at the Illinois border, virtually an extension of the Illinois Northwest Tollway. Interstate 90 in Wisconsin was completed in 1969.

Illinois

    I-90 in Illinois is 103 miles long from the Wisconsin border to the Indiana border. I-90 is technically not complete from coast to coast due to the Chicago Skyway which presently does not meet current interstate standards. The 8 mile viaduct by-pass takes traffic from downtown Chicago to the Indiana border. Most of I-90 in Illinois is part of the Northwest Tollway. Some sections of these toll roads were completed before the Interstate Highway Act in 1956.

Indiana

    I-90 in Indiana is 157 miles long from the Illinois border to the Ohio border. I-90 shares the same stretch of road with I-80 from Exit 21 in Freemont, IN across most of northern Indiana to the Ohio border. Between LaPort, IN and Toledo, OH with I-80 it is not more than ten miles from the Michigan border. I-90 in the western end of Indiana passes through a heavily industrialized area. I-90 is part of the Indiana Toll Road passing through the Eastern Great Lakes Lowland region.

Ohio

    I-90 in Ohio is 244 miles long from the Indiana border to the Pennsylvania border. I-90 continues to share the same road with I-80 on the James W. Shocknessy Ohio Turnpike which was opened in 1955. I-90 continues through the Eastern Great Lakes Lowland which can be described in one word, flat.

Pennsylvania

    Intersections with other Interstates:
  • I-79 in Erie

    I-90 in Pennsylvania is 47 miles long from the Ohio border to the New York border. First called the Erie County Thruway when it first opened in Oct. 1960, it is now known as the Amvet Memorial Highway. It was originally destined to be part of the Pennsylvania Turnpike until the Eisenhower Interstate System bill was signed in 1956. The PTC packed up all the plans and sent them to the Pennsylvania Dept. of Highways giving them a nice headstart on having the first stretch of I-90 to be completed in any state. (All 47 miles.)

New York

    I-90 in New York is 391 miles long from the Pennsylvania border to the Massachusetts border. The exit numbers start in Yonkers, New York close to the Bronx and are numbered in chronological order to Albany, then east to Buffalo and down the Lake Erie shoreline to the PA border. So if you are traveling east the exit numbers start at Exit 61 near Ripley, NY and go backwards to Exit 1 in Yonkers.

    I-90 follows the 70 mile Buffalo Section from the Pennsylvania border to Buffalo. It then follows the Thomas E. Dewey New York State Thruway east on The Mainline section for 297 miles and the last 24 miles follow the Berkshire Section to the Massachusetts border. At one time there were two metric signs in the westbound lanes near Syracuse, NY. They were speed limit signs which read 88 km/hr. They were part of a metric signage test. Rumor has it that a state representative who lives near Syracuse opposed the idea so the signs were put there in jest. Some sections of the New York Thruway were completed before the Interstate Highway Act of 1956 and thus predate the Interstate 90 designation.

Massachusetts

    I-90 in Massachusetts is 160 miles long from the New York border to Logan Airport. Interstate 90 passes through western Massachusetts in the Berkshire Hills and continues straight through to Boston. This last section of the interstate is the Massachusetts Turnpike. The exit numbers go in chronological order from west to east. The eastern terminus is now at Logan Airport.


Sources:

Interstate 90 @ Interstate-Guide.com (http:www.interstate-guide.com/i-090.html)
Interstate 90 - Wikipedia, the free encylopedia (http://en.wikipedia.org/wiki/Interstate_90)
Interstate 90 (http://www.ihoz.com/I90.html)
Northwest Highways I-90 page (http://nwhighways.amhosting.net/i90page.html)
Interstate 90 in the Sheridan, Wyoming area (http://www.northwestplaces.com/tripsWY/Sheridan1090.htm)
South Dakota Highways 61-100 (http://www.dm.net/~chris-g/sd61-100t.html)
Details of Routes 76-100 (http://www.steve-riner.com/mnhighways/r76-100.htm)
Wisconsin State Highways (76-100) (http://members.aol.com/WisconsinHwys/WiscHwys76-100.html)
Pennsylvania Highways: Interstate 90 (http://www.pahighways.com/interstates/I90.html)
NYS Thruway Fact Book (http://www.thruway.state.ny.us/factbook/)

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