|Length:||3,101.13 mi (4,990.78 km)|
|Existed:||1956 – present|
|West end:||SR 519 or 4th Ave S in Seattle, WA|
I-65 in Gary, IN
I-75 near Toledo, OH
I-87 / Thruway in Albany, NY
I-95 in Weston, MA
|East end:||Route 1A in Boston, MA|
Interstate 90 (I-90) is the longest Interstate Highway in the United States of America at 3,101.13 miles (4,990.78 km). It is the northernmost coast-to-coast interstate, and parallels US 20 for the most part. Its western terminus is in Seattle, Washington, at Edgar Martinez Drive S. near Safeco Field and CenturyLink Field, and its eastern terminus is in Boston, Massachusetts, at Route 1A near Logan International Airport. Interstate 90 crosses the Continental Divide over Homestake Pass just east of Butte, Montana.
East of the Wisconsin-Illinois border, much of I-90 is tolled, along the following toll roads (several of which predate the Interstate system): the Jane Addams Memorial Tollway, Chicago Skyway, Indiana Toll Road, Ohio Turnpike, New York State Thruway, and the Massachusetts Turnpike, including the Ted Williams Tunnel. It is free through downtown Chicago; Greater Cleveland and the rest of Northeast Ohio; Pennsylvania; and through brief sections near Buffalo, Albany, and Boston.
Route description 
The western I-90 terminus is in the SoDo neighborhood of Seattle, Washington. I-90 eastbound begins at exit 2B, Edgar Martínez Drive S and 4th Avenue S. I-90 westbound exit 2B ends at Edgar Martínez Dr and 4th Ave near Safeco Field, as well as 4th Ave just north of S. Royal Broughman Way near CenturyLink Field, about a block east of the entrance to the Port of Seattle's container shipping terminal 46.
The tunnel that carries Interstate 90 under the Mount Baker Ridge is on the National Register of Historic Places. The east portal of the tunnel (visible when entering Seattle from the east) is constructed as a bas relief concrete sculpture.
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 Mercer Island, Washington. They are the second and fifth longest such bridges, respectively.
Forty miles east of Bellevue I-90 traverses the Cascade Range's Snoqualmie Pass, elevation 3,022 feet (921 m). At mile post 137, it crosses the Columbia River on the Vantage Bridge, and after entering Spokane, Washington near mile post 279, enters Idaho 18 miles (29 km) later.
Washington Law Defining Route
The Washington section of I-90 is defined in the Revised Code of Washington (RCW 47.17.140).
The small town of Wallace, Idaho still prides itself on having what was the last stop light on I-90. Its downtown has many historical buildings, which would have been wiped out by the original planned route of the freeway, so in 1976, city leaders had the downtown placed on the National Register of Historic Places. As a result, the federal government was forced, at great expense, to reroute the freeway to the northern edge of downtown and elevate it. That section of I-90 opened in September 1991. A bicycle path is routed beneath part of that segment.
From 1995 until 1999, there was no numbered speed limit on I-90 in Montana. The speed limit was simply defined as "reasonable and prudent" as determined on a case by case basis by the Montana Highway Patrol. The speed limit in Montana is now 75 mph (120 km/h). From the west I-90 enters Montana on the summit of Lookout Pass. It passes next to Missoula and runs through Butte (connecting with Interstate 15 for close to 8 miles) before crossing the continental divide just east of Butte where it goes over Homestake Pass, which is 6,329 feet (1929 m.) in elevation, the highest point for the Interstate. It passes between the Gallatin and Bridger mountain ranges over Bozeman Pass between Bozeman and Livingston. It follows the Yellowstone River from Livingston to Billings where it connects the suburbs of Laurel and Lockwood with the rest of the Billings. In Lockwood it intersects with I-94's western terminus and turns south. South of Hardin it passes the site of the Battle of the Little Bighorn (Custer's Last Stand) at Crow Agency on the Crow Indian Reservation. Montana boasts the longest stretch of I-90, ranging just over 551 miles (887 km).
I-90 enters the state of Wyoming from the north after splitting off from I-94 in Billings, MT. The first major town is Sheridan where it heads southbound. It then follows the foothills of the Bighorn Mountains between Sheridan and Buffalo where it then intersects with I-25, where the route goes from a north–south orientation to an east–west orientation. It then goes across the Powder River Basin toward Gillette, Moorcroft, and Sundance where it shares alignments with both US 14 and US 16.
South Dakota 
Near Rapid City, South Dakota at the Wyoming border I-90 is a four lane divided highway with a grass median. In the Sioux Falls area, I-90 intersects I-29 and continues east a short distance to Minnesota. I-90 is the longest east–west thoroughfare in South Dakota. This interstate goes through Mitchell, Sioux Falls, and Rapid City. It does not go through the state capital of Pierre.
The South Dakota section of I-90 is defined at South Dakota Codified Laws § 31-4-184.
The Minnesota section of I-90 is defined as Route 391 in Minnesota Statutes § 161.12(3).
I-90 crosses southern Minnesota from the South Dakota border near Beaver Creek, Minnesota, to the Mississippi River near La Crosse, Wisconsin. On most of its length in the state, it is close to the Iowa border and fairly parallel with it. In southeast Minnesota, it curves north to Rochester and Winona.
The wayside rest area near Blue Earth, Minnesota, is where the east-building I-90 and west-building I-90 teams linked up in 1978, thus completing the final mile and joining the 3,099.07 miles (4,987.47 km) of the interstate. Since being overlaid with bituminous paving in 2006, the original 4-foot-wide (1.2 m) gold colored cement concert line marking the completion of I-90 has been replaced with gold paint on just the shoulder portions of the roadway at the same location; plaques dedicating and describing this special segment of I-90 pavement can be found at the Blue Earth rest areas.
At the Minnesota-Wisconsin border I-90 is carried on a high bridge over the upper Mississippi River, departing La Crescent MN and entering LaCrosse WI. The route uses French Island for part of its ford over the Mississippi. Below the bridge is a lock and dam on the river.
I-39/90/94 from just south of Portage to Madison is the longest concurrency of three Interstate Highways in the United States.
In the state of Illinois, Interstate 90 enters Illinois north of Rockford oriented north–south joined with Interstate 39. It then runs east-southeast directly to the city of Chicago. From Rockford to Interstate 294 the road is tolled and called the Jane Addams Memorial Tollway. Prior to 2007 the Jane Addams Memorial Tollway was called the Northwest Tollway. In the Chicago metropolitan area, I-90 is known by three names from O'Hare International Airport to the Indiana state line. The Kennedy Expressway runs from O'Hare to Interstate 290 and the Chicago Loop. I-90 continues running south of the Loop on part of the Dan Ryan Expressway, and then southeast onto the tolled Chicago Skyway into Indiana.
In the state of Indiana, the entirety of Interstate 90 is concurrent with the Indiana Toll Road. Interstate 90 enters from Illinois at the Chicago Skyway. It then runs to the concurrency of Interstates 80/94 east of Interstate 65, where I-80 leaves I-94 and joins with I-90. The combined I-80/90 route runs east across northern Indiana and near the southern border of Michigan to the Ohio state line.
The Indiana Toll Road turns into the Ohio Turnpike as it crosses the border. I-90 follows the Ohio Turnpike until Lorain (west of Cleveland), where it turns north to follow a route near the shores of Lake Erie. Originally, it was going to be parallel to, and north of, I-80/Ohio Turnpike further west to Toledo. Parts were built with an interim assignment of State Route 2. Later; that plan was abandoned, and the I-90/I-80 exit/connector was built instead; those existing parts retain the Rt. 2 designation.
In Cleveland, Interstate 90 serves as the Innerbelt at the confluence of the northern termini of Interstates 71 and 77. One of the most peculiar and hazardous stretches of Interstate 90 is the section of highway passing through downtown, known locally as Dead Man's Curve. Here, the road takes a nearly 90-degree turn. While there are plenty of large signs, flashing lights, and rumble strips alerting motorists to this turn, there have still been a large number of accidents resulting from inattentive motorists. There are plans to realign the freeway along a shallower curve within the next decade, as part of a larger project to improve the highway system in Cleveland.
The Innerbelt in Cleveland also utilizes a steel-gusset bridge of the same design as the I-35W bridge that failed in Minneapolis, Minnesota. Since September 30, 2008, two lanes in each direction of the 8-lane bridge were closed to reduce the weight load on the structure. The bridge is currently under close inspection as it has deteriorated greatly over the last few years. On October 8, 2008, the bridge was closed entirely to undergo a stress test. In May and June 2009, the bridge was closed while engineers lifted it with hydraulic jacks and moved it approximately six inches to realign it. It is largely believed that the bridge will be replaced within the next five years by a new span. Many in the Cleveland area are beginning to question the safety of the bridge, and the Ohio Department of Transportation continues to stress that the bridge is safe and if there was any imminent danger it would be permanently closed. There are plans to build a new bridge which will carry I-90 west and I-71 south. The old bridge will carry I-71 north and I-90 east. Construction is now underway on the new bridge trusses. The project started in late 2010 and will wrap up in about 3 to 4 years. as stated by ODOT.
In Pennsylvania, I-90, called the "AMVETS Memorial Highway" (also signed as such in New York state), is a non-tolled section that extends from the Ohio state line through to New York state going through Erie, Pennsylvania. Although, this was supposed to be the "Erie Extension" of the Pennsylvania Turnpike, it was however completed in 1958 with funding from the Pennsylvania Turnpike Commission. Because Ohio had built their portion of the highway prior to the opening of this section, cars were dumped at an exit in Petersburg, Ohio. When this portion of the highway was open, the speed limit was 50 miles per hour. At 46.4 miles (74.67 km), it is Interstate 90's shortest intrastate length.
In 2007, a major pileup forced a 15 hour closure of the entire stretch in Pennsylvania due to winter storm white out conditions.
While not an interstate, a portion of Pennsylvania Route 5 in Erie has recently been named Pennsylvania Route 290. This route utilizes a stretch of Erie's 12th Street as a loop, connecting Interstate 79 and 90 to the Bayfront Connector and downtown Erie. Besides this, there are no auxiliary routes signed in Pennsylvania.
New York 
I-90 becomes the New York State Thruway upon entering New York. Between the Pennsylvania state line and the Syracuse interchange, it is also signed as the "AMVETS Memorial Highway". It follows the Lake Erie coast until Buffalo, where it joins the old Water Level Route until Albany. There, it takes a short detour before joining the New York State Thruway Berkshire Connector.
Almost all of the New York portion of the road is a toll road, comprising the east–west portion of the New York State Thruway mainline and part of the Berkshire Connector, 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 road roughly follows the course of the 19th-century Erie Canal for much of its length in New York State. "I-90" (operated by NYSDOT) carries Interstate 90 between the two; however, the Berkshire Section directly connects to the mainline (at Thruway interchange 21A) 6.5 miles (10.5 km) west of the point where I-90 joins it (at Thruway interchange B1).
The mileposts and exit numbers on the New York State Thruway mainline originate at the New York City line and increase northward along Interstate 87 and westward along Interstate 90. As a result, mileposts and exit numbers on the I-90 section of the Thruway mainline increase from east to west, contrary to modern practices where numbers increase from the west or south. The NYSDOT-maintained portion in between, known to locals as "I-90," does number its mileage and exits in the traditional west-to-east method. (Ironically, the NYSDOT maintained portion of I-90 is oriented geographically north–south for most of its length, so the exit numbers seem to increase from north to south.) Exit and milepost numbering starts over again when the Berkshire Section of the Thruway begins, with exit and mile numbers preceded by the letter B (Exit B1, Exit B2, Mile B1, Mile B2, and so on).
There once were two metric-only signs on the westbound New York State Thruway around Syracuse, which is about 100 miles (161 km) from Ontario. The NYS Thruway Authority decided to test metric signage, which may have briefly included 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. These signs are now displayed in just miles.
I-90 is currently the only Interstate having a complete set of nine spur routes (190, 290, 390...890, 990) within one state, in New York. Interstate 80 formerly did in California, but no longer. In addition, I-990, a short spur route near Buffalo, New York not directly connected to I-90, is the highest number given to an Interstate.
I-790 in Utica used to have a completely direct connection with I-90 at Thruway interchange 31. Various road redesign projects over the years have eventually led to this direct connection being partially severed. Traffic exiting the Thruway must use two different surface streets to reach I-790. However, it is still possible to travel from I-790 directly onto the Thruway. I-790 has some other oddities: no exit numbers, no reassurance markers, and it runs concurrent with New York State Route 5 for its entire length.
The first section of the Boston Extension opened in September 1964 from the original terminus at Route 128 to the Allston/Brighton Tolls. The entire Boston Extension opened on February 18, 1965 continuing from the Allston/Brighton Tolls to I-93 in Downtown Boston. The new extension added 12 miles (19 km) to the MassPike's original 123.
I-90 was extended again as part of the Big Dig from its terminus at I-93 to Boston's Logan International Airport and a terminus of Route 1A in January 2003 via tunnels under the Fort Point Channel and the Ted Williams Tunnel under Boston Harbor. This extended I-90 by an additional 2.3 miles (3.7 km), shifting the eastern terminus to Route 1A.
Tractors with two 48-foot (15 m) trailers ("turnpike doubles") are permitted to travel between exit 11 and through the New York state border.
I-90 made heavy use of existing roads. The Massachusetts Turnpike, New York State Thruway, Ohio Turnpike, Indiana Toll Road, Chicago Skyway, and the Jane Addams Memorial Tollway all predate I-90 and were used for parts of its route. This also means that substantial portions of the route are not precisely to Interstate Highway standards, but they are usually close.
The popular TV sitcom Cheers was set in Boston, on the east end of I-90. When the spin-off Frasier was being developed, it was decided to set that series as far from Boston as possible, so Seattle, on the west end of I-90, was chosen as the setting.
Major intersections 
- Interstate 5 in Seattle, Washington
- Interstate 405 in Bellevue, Washington
- Interstate 82 in Ellensburg, Washington
- Interstate 15 in Butte, Montana; joined for 7.65 miles (12.31 km)
- Interstate 94 in Billings, Montana
- Interstate 25 in Buffalo, Wyoming
- Interstate 29 in Sioux Falls, South Dakota
- Interstate 229 in Sioux Falls, South Dakota
- Interstate 35 in Albert Lea, Minnesota
- Interstate 94 in Tomah, Wisconsin; joined for 91.76 miles (147.67 km) until Madison, Wisconsin.
- Interstate 39 in Portage, Wisconsin; joined for about 95 miles (152 km) until Rockford, Illinois.
- Interstate 43 in Beloit, Wisconsin
- Interstate 94 in Chicago, Illinois; joined for 16.71 miles (26.89 km)
- Interstate 55 in Chicago, Illinois
- Interstate 65 in Gary, Indiana
- Interstate 94 in Lake Station, Indiana
- Interstate 80 in Lake Station, Indiana; joined for 278.40 miles (448.04 km) until Lorain, Ohio.
- Interstate 69 in Fremont, Indiana
- Interstate 75 in Toledo, Ohio
- Interstate 71 in Cleveland, Ohio
- Interstate 77 in Cleveland, Ohio
- Interstate 271 in Willoughby, Ohio
- Interstate 79 in Erie, Pennsylvania
- Interstate 86 in Erie, Pennsylvania
- Interstate 81 in Syracuse, New York
- Interstate 88 in Rotterdam, New York
- Interstate 87 in Albany, New York
- Interstate 91 in West Springfield, Massachusetts
- Interstate 291 in Chicopee, Massachusetts
- Interstate 84 in Sturbridge, Massachusetts
- Interstate 395 in Auburn, Massachusetts
- Interstate 495 in Hopkinton, Massachusetts
- Interstate 95 in Weston, Massachusetts
- Interstate 93 in Boston, Massachusetts
Auxiliary routes 
- Rapid City, South Dakota - I-190
- Chicago, Illinois - I-190 (provides a direct route to O'Hare International Airport), I-290
- Cleveland, Ohio - I-490
- Buffalo, New York - I-190, I-290, I-990 (not directly connected)
- Rochester, New York - I-390, I-490, I-590 (not directly connected)
- Syracuse, New York - I-690
- Utica, New York - I-790
- Schenectady, New York - I-890
- Spur to I-495 in Marlborough, Massachusetts - I-290
- Spur to Leominster, Massachusetts - I-190
I-90 is the only interstate to have a complete set of auxiliary routes (i.e., all nine possible three-digit route numbers) within a single state, that being New York.
- "FHWA Route Log and Finder List". U.S. Department of Transportation. Retrieved 2009-08-08.
- "Mountains To Sound Greenway (Washington)".
- "RCW 47.17.140 State route No. 90 — American Veterans Memorial Highway". Access Washington -- Official State Government Website. Retrieved 2007-08-29.
- "South Dakota Codified Laws". South Dakota Legislature - Legislative Research Council. Retrieved 2007-08-29.
- "161.12, Minnesota Statutes 2006". Minnesota State Legislature, Office of the Revisor of Statutes. 2006. Retrieved 2007-08-29.
- "MINNESOTA HIGHWAYS". Retrieved 2013-01-29.
- "Construction Project Log Record". Retrieved 2013-01-29.
- Google Inc. Google Maps – Cleveland, Ohio satellite view (Map). Cartography by Google, Inc. http://maps.google.com/maps?q=Cleveland,+OH&t=h&hl=en&ll=41.515872,-81.672256&spn=0.011809,0.029697&om=1. Retrieved 2007-08-29.
- "Cleveland Urban Core Projects". Ohio Department of Transportation. Retrieved 2007-08-29.
- "AMVETS Memorial Highway". Retrieved 2012-06-02.
- "I-90 Reopens After Fatal Crash Near Erie, Pennsylvania". Retrieved 2012-06-02.
- "(Title Forthcoming)". Retrieved 2007-08-29.
|Wikimedia Commons has media related to: Interstate 90|
- Geographic data related to Interstate 90 at OpenStreetMap
- Illinois Highway Ends: I-90
- Indiana Highway Ends: I-90
- I-90 (Greater New York Roads)