I-90

I-90 is a major transcontinental Interstate Highway in the United States, spanning approximately 3,020 miles from Seattle, Washington, to Boston, Massachusetts. It is the longest Interstate Highway in the country, traversing 13 states and connecting major cities such as Spokane, Billings, Sioux Falls, Chicago, Cleveland, and Buffalo. The highway serves as a critical artery for cross-country commerce, tourism, and transportation, passing through diverse landscapes including the Cascade Range, the Great Plains, and the Appalachian Mountains.

Route description

Beginning at an interchange with SR 519 near Elliott Bay in downtown Seattle, the route travels east across Washington on the Washington segment, crossing the Cascade Range via Snoqualmie Pass. It continues through the Columbia River basin into Idaho, passing south of Coeur d'Alene and through Post Falls. In Montana, it follows a path north of the Yellowstone River, skirting the Beartooth Mountains and serving Billings and Bozeman. The highway crosses the Continental Divide at Homestake Pass before entering Wyoming near Sheridan and briefly passing by Devils Tower National Monument.

Entering South Dakota, it runs just north of the Badlands National Park and near Mount Rushmore in the Black Hills. It crosses into Minnesota at La Crosse on a bridge over the Mississippi River, then cuts across the southeastern corner of the state into Wisconsin. It serves Madison and Milwaukee before descending into Illinois as the Jane Addams Memorial Tollway, a key route into Chicago and along the shore of Lake Michigan. From Indiana through Ohio, it parallels the Ohio Turnpike, passing south of Cleveland and through Akron.

In Pennsylvania, it becomes the Keystone Shortway, crossing the Allegheny Mountains before entering New York south of Buffalo. It follows the New York State Thruway corridor, passing near Rochester and Syracuse before crossing into Massachusetts via the Berkshire Mountains. Its eastern terminus is in Boston at a junction with MA 1A and Logan International Airport.

History

The highway's origins lie in the Federal-Aid Highway Act of 1956, which authorized the construction of the Interstate Highway System. Many segments were built over existing roadways, such as the Massachusetts Turnpike and the Indiana Toll Road. A significant engineering achievement was the 1979 completion of the second floating bridge across Lake Washington in Seattle, replacing the original Lacey V. Murrow Memorial Bridge. The final section to be completed was a segment through South Dakota's Black Hills, finished in the late 1980s, which included the impressive Michael J. Kirwan Memorial Bridge over the Grand River.

Major intersections

Key junctions include its western terminus at SR 519 in Seattle and its eastern terminus at MA 1A in Boston. Major interchanges occur with I-5 in Seattle, I-15 in Butte and Salt Lake City, I-29 in Sioux Falls, I-35 in Minneapolis–Saint Paul, I-94 in Madison and Chicago, I-65 in Gary, I-71 in Cleveland, I-79 in Erie, and I-87 (the New York State Thruway) near Albany. It also meets I-95 in Weston, providing a critical link to the Atlantic coast.

Auxiliary routes

Several three-digit auxiliary routes serve metropolitan areas along the corridor. These include I-190 and I-290 in the Chicago area, I-190 providing access to Worcester, and I-290 (the Worcester–Boston corridor). In New York, I-190 branches north to Niagara Falls, while I-390 provides a route toward Corning. I-490 forms a beltway around Cleveland, and I-190 is a short spur into Rapid City.

Exit list

A comprehensive exit list details every interchange along its entire length, beginning with Exit 1 in Seattle at 4th Avenue South and proceeding eastward. Notable exits include those for Snoqualmie Pass, Spokane, Missoula, the Little Bighorn Battlefield National Monument, Wall Drug, the Minnesota–Wisconsin border at the Mississippi River, O'Hare International Airport, the Indiana Toll Road main gate, the Rock and Roll Hall of Fame in Cleveland, the Pro Football Hall of Fame in Canton, Pymatuning State Park, and the final exits in Boston near the Ted Williams Tunnel and Logan International Airport.