Interstate 90

Interstate 90 (I-90) is the major Interstate Highway in the northern United States. It is the northernmost east–west transcontinental freeway, and the longest Interstate Highway in the United States at 3,020.54 miles (4,861.09 km). Its western terminus is in Seattle, at State Route 519 near T-Mobile Park and CenturyLink Field, and its eastern terminus is in Boston, at Route 1A near Logan International Airport.

The western portion of I-90 crosses the Continental Divide over Homestake Pass just east of Butte, Montana, connecting major cities such as Spokane, Washington; Billings, Montana; Sioux Falls, South Dakota; and Madison, Wisconsin.

Between Seattle and the Wisconsin-Illinois state line, I-90 is a toll-free Interstate. East of that border, much of I-90 follows several toll roads, many of which predate the Interstate Highway system. These include the Jane Addams Memorial Tollway, Chicago Skyway, Indiana Toll Road, Ohio Turnpike, New York State Thruway, and the Massachusetts Turnpike. The Interstate is not tolled through some segments in downtown Chicago; Greater Cleveland and the rest of Northeast Ohio; Erie and the rest of Northwestern Pennsylvania; and through brief sections near Buffalo and Albany in New York.

I-90 is one of the oldest interstate highways. It passes through 13 states, the second most following I-95, which serves 15 states (excluding a brief route in District of Columbia). The states I-90 serves includes Washington, Idaho, Montana, Wyoming, South Dakota, Minnesota, Wisconsin, Illinois, Indiana, Ohio, Pennsylvania, New York, and Massachusetts.

I-90 passes through the cities of Seattle, Spokane, Coeur d'Alene, Billings, Sioux Falls, Madison, Chicago, Gary, Toledo, Cleveland, Erie, Buffalo, Rochester, Syracuse, Utica, Schenectady, Albany, and Boston. I-90 is a cross-country freeway known as the Washington Highway.

Route description

Washington

The western I-90 terminus is in the SoDo neighborhood of Seattle. I-90 eastbound begins at exit 2B, Edgar Martínez Drive S (State Route 519) and 4th Avenue S. I-90 westbound exit 2B ends at Edgar Martínez Dr and 4th Ave near T-Mobile Park, as well as 4th Ave just north of S. Royal Brougham Way near CenturyLink Field, about a block east of the entrance to the Port of Seattle's container shipping terminal at Pier 46.

The tunnel that carries I-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. They are the second and fifth longest such bridges, respectively.

Forty miles (64 km) east of Bellevue, I-90 traverses the Cascade Range's Snoqualmie Pass, elevation 3,022 feet (921 m). It intersects I-82 shortly after exiting the mountains and crosses the Columbia River on the Vantage Bridge at mile post 137. After entering Spokane near mile post 279, it enters Idaho eighteen miles (29 km) later.

Since 1980, I-90 from Seattle to Thorp was designated the Mountains to Sound Greenway to protect its outstanding scenic and cultural resources.

The Washington section of I-90 is defined in the Revised Code of Washington (RCW 47.17.140)

Indiana

Main Article: Indiana Toll Road

New York

I-90 runs concurrently with the New York State Thruway upon entering the state of 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 along the Rensselaer County Veterans Memorial Highway 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 I-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 I-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 I-87 and westward along I-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. Coincidentally, 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, etc.)

There once were two metric-only signs on the westbound New York State Thruway around Syracuse, which is about 100 miles (160 km) from Ontario. The NYS Thruway Authority decided to test metric signage, which may have briefly included an 88 km/h (55 mph) speed limit sign, on the Thruway. There was also a sign displaying the distance to the I-81 interchange in kilometers in DeWitt. These signs are now only displayed in mile figures.

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. I-80 in California has had all nine, but never all at the same time. 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 concurrently with New York State Route 5 (NY 5) for its entire length.

The New York section of I-90 west of the Berkshire Section of the New York Thruway is defined as Interstate Route 504 in New York Highway Law § 340-a.

Massachusetts

Main Article: Massachusetts Turnpike.

I-90 in Massachusetts runs concurrently with the pre-Interstate-era Massachusetts Turnpike (known locally as "the Pike" or on signs as "MassPike"), which opened on May 15, 1957, from West Stockbridge at the New York state border to Route 128.

Interstate Highway System

Major Interstates are written in bold.