Is I-90 a freeway or a highway?

Interstate 90 is both: it is an Interstate Highway that is built and operated as a controlled-access freeway along virtually its entire route from Seattle, Washington, to Boston, Massachusetts. In U.S. road terminology, “highway” is the broad category, while “freeway” describes I-90’s design: fully grade-separated interchanges, no traffic signals, and limited access.

What I-90 is—and why the terms can be confusing

I-90 is the longest route in the U.S. Interstate Highway System, stretching roughly 3,020 miles coast to coast. Because “highway” refers broadly to significant public roads and “freeway” refers to a specific limited-access design standard, both labels can be accurate depending on context. In practice, I-90 functions as a freeway for its entire length, meeting Interstate design standards with interchanges instead of intersections and controlled entry/exit points.

Freeway versus highway: how I-90 fits the definitions

To clarify what makes I-90 a freeway, it helps to break down the features that define these terms and how the route complies with modern standards.

• Freeway: a controlled-access road with grade-separated interchanges, no at-grade crossings, and no traffic signals or direct driveway access.
• Highway: a broad term for major public roads; can include freeways, expressways, and conventional highways with intersections.
• Interstate Highway: a federally designated network built to freeway standards, with occasional historical exceptions that have been largely eliminated through upgrades.

By these definitions, I-90 is unequivocally a freeway and, more generally, an Interstate Highway. While temporary construction work zones can create lane crossovers or reduced speeds, the route remains access-controlled.

Route overview and length

I-90 runs east–west from downtown Seattle—crossing Lake Washington via two floating bridges—through the northern tier of the country to downtown Boston. The corridor supports long-haul freight, regional commuting, and cross-country travel, traversing mountain passes, plains, lakeshores, and dense urban centers.

States traversed

The following list shows the states that I-90 passes through, illustrating its nationwide footprint and the diversity of terrain and jurisdictions it connects.

• Washington
• Idaho
• Montana
• Wyoming
• South Dakota
• Minnesota
• Wisconsin
• Illinois
• Indiana
• Ohio
• Pennsylvania
• New York
• Massachusetts

This 13-state span underscores I-90’s role as a true transcontinental freeway, linking the Pacific Northwest to New England through major metropolitan areas and vast rural corridors.

Key features and notable segments

Several stretches of I-90 are notable for their engineering, traffic role, or tolling practices, reflecting how a single freeway can operate under multiple authorities while maintaining consistent access-control standards.

• Seattle area: crosses Lake Washington via the Lacey V. Murrow and Homer M. Hadley floating bridges, a rare engineering feature for an Interstate.
• Mountain passes: includes Washington’s Snoqualmie Pass and Montana’s high-altitude segments, designed to Interstate safety standards with seasonal weather operations.
• Toll segments: includes the Massachusetts Turnpike, New York State Thruway (including the Berkshire Spur), Ohio Turnpike, Indiana Toll Road, and the Chicago Skyway.
• Urban expressways: the Dan Ryan and Kennedy Expressways in Chicago carry I-90 through one of the nation’s busiest corridors.
• Rural mobility: long free-flow segments across South Dakota, Minnesota, and Wyoming facilitate cross-country freight and travel.

Across these varied contexts, I-90 maintains freeway characteristics—interchanges, ramps, and barriers separating opposing traffic—regardless of whether a segment is tolled or free to use.

Why the question comes up

People often ask whether a specific route is a freeway or a highway because everyday language blurs the distinction. “Highway” can refer to any major road, but in transportation planning, “freeway” signals a design that optimizes speed and safety through access control. Since I-90 is designated as an Interstate Highway and built to freeway standards, both labels apply—though “freeway” best describes its operational design.

Bottom line

I-90 is an Interstate Highway and, functionally, a freeway end to end. It offers controlled, grade-separated travel with no traffic signals, meeting the core standards of the Interstate system across its 13-state, coast-to-coast route.

Summary

I-90 is both: it is an Interstate Highway built and operated as a controlled-access freeway across roughly 3,020 miles from Seattle to Boston. In U.S. road terminology, “highway” is the broad category, while “freeway” describes I-90’s design—no at-grade intersections, no traffic lights, and access limited to interchanges—even as it passes through diverse terrains, major cities, and both tolled and non-tolled segments.