Which U.S. interstate runs from Boston, Massachusetts to Seattle, Washington?

Which U.S. interstate runs from Boston, Massachusetts to Seattle, Washington? The answer is Interstate 90.

I-90 crosses the northern United States from Seattle to Boston, covering about 3,100 miles. It passes through 13 states, including Washington, Montana, Wyoming, South Dakota, Minnesota, Wisconsin, Illinois, Indiana, Ohio, Pennsylvania, New York and Massachusetts. The route connects major cities such as Chicago, Cleveland and Buffalo while crossing the Cascades and Rocky Mountains.

The highway was authorized under the Federal-Aid Highway Act of 1956 and numbered in 1957. It incorporated several major toll roads that predated the Interstate system, including the Indiana Toll Road, Ohio Turnpike, New York State Thruway and Massachusetts Turnpike. The final piece near Seattle opened in 1993.

A common mix-up is direction: although people often describe the route as running from Boston to Seattle, its signed western terminus is in Seattle and its eastern terminus is near Boston’s Logan International Airport. I-90 is also the longest Interstate Highway, while I-80 is another major coast-to-coast route farther south.