Guide Rankings Geography Updated June 3, 2026

Pacific Northwest States: Full List, Core States, and Borderline Cases

Mount Rainier reflected in a subalpine lake in Washington State, surrounded by old-growth forest

Pacific Northwest States: Full List, Core States, and Borderline Cases

Ranking - Geography

Washington is one of two states included in every definition of the Pacific Northwest. Mount Rainier, at 14,411 feet, is the highest peak in the Cascade Range and the dominant geographic landmark of the region.

Quick Answer

Pacific Northwest States: Full List, Core States, and Borderline Cases

  1. 1

    Washington and Oregon are the only two states included in every definition of the Pacific Northwest — from the narrowest federal agency boundary to the broadest geographic usage. No other state appears in all sources.

  2. 2

    Idaho is in most definitions of the Pacific Northwest — including EPA Region 10 and Wikipedia — but is excluded from the narrowest definitions (such as the U.S. Forest Service Region 6, which covers only Washington and Oregon). Idaho has no Pacific coastline, which is the most common reason for its exclusion.

  3. 3

    No federal authority defines the Pacific Northwest with the same boundary. The U.S. Forest Service uses 2 states (WA, OR). The EPA uses 4 states (WA, OR, ID, AK). Wikipedia and most travel and media sources use 3 states (WA, OR, ID). Western Montana and far northern California appear in geographic and ecological definitions but not in any agency's Pacific Northwest boundary.

Map

Pacific Northwest States Map

Pacific Northwest
No data
Washington and Oregon (darkest green) are the only states in every definition. Idaho (medium green) is in most. Western Montana and far northern California (lightest) appear only in ecological or geographic definitions and are excluded from all federal agency boundaries.
Pacific Northwest States Map
Rank State Pacific Northwest
1 Montana 1
2 California 1
3 Oregon 3
4 Idaho 2
5 Washington 3

Washington and Oregon (darkest green) are the only states in every definition. Idaho (medium green) is in most. Western Montana and far northern California (lightest) appear only in ecological or geographic definitions and are excluded from all federal agency boundaries.

Pacific Northwest States: Full List, Core States, and Borderline Cases Table

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Clean, print-ready version of Pacific Northwest States: Full List, Core States, and Borderline Cases.

What States Are in the Pacific Northwest?

Mount Rainier reflected in a subalpine lake surrounded by old-growth forest in Washington State
Mount Rainier (14,411 feet) is the highest peak in the Cascade Range, the mountain chain that runs the length of Washington and Oregon and defines the climate divide between the wet Pacific Northwest coast and the arid interior.

Washington and Oregon are the only two states in every definition of the Pacific Northwest — the one point all sources agree on. Idaho is in most definitions, including EPA Region 10 and Wikipedia, giving a standard 3-state U.S. core. Western Montana and far northern California appear in geographic and ecological definitions but are excluded from all federal agency boundaries. British Columbia is the Canadian portion of the region included in most broad definitions.

The disagreement exists because the Pacific Northwest has no statutory or Census definition. Unlike the Appalachian Region (defined by Congress and the ARC) or New England (a fixed 6-state Census division), the Pacific Northwest is a cultural and geographic concept with no authoritative boundary. Each agency and reference draws the line differently based on its own purpose.

How Federal Agencies and Major Sources Define the Pacific Northwest

The U.S. Forest Service uses the narrowest definition: its Pacific Northwest Region (Region 6) covers Washington and Oregon only. The EPA uses the broadest federal definition: Region 10 covers Washington, Oregon, Idaho, and Alaska. The Census Bureau's Pacific division — which groups states for statistical purposes — covers Washington, Oregon, California, Hawaii, and Alaska, omitting Idaho entirely and adding states no one considers Pacific Northwest culturally.

Wikipedia, WorldAtlas, and most travel and media organizations use a middle definition of 3 states: Washington, Oregon, and Idaho. This is the most common answer to 'what states are in the Pacific Northwest' across reference sources. Britannica describes the region as Washington, Oregon, and 'part of' Idaho — acknowledging that eastern Idaho is culturally and geographically distinct from the western part of the state that connects to the Pacific Northwest.

Why Washington and Oregon Are the Undisputed Pacific Northwest Core

Columbia River Gorge seen from the Oregon side, with basalt cliffs and the river below
The Columbia River forms much of the border between Oregon and Washington and drains most of Idaho — connecting all three core Pacific Northwest states in a single watershed. The Columbia is the hydrologic basis for grouping Idaho with Washington and Oregon.

Washington and Oregon share three defining characteristics no other U.S. state replicates together: Pacific Ocean coastline, the Cascade Range as a dominant interior divide, and a west-of-Cascades temperate rainforest climate. This combination — wet coast, mountain spine, arid interior — defines the Pacific Northwest landscape more precisely than any political boundary. Both states have been grouped together since the Oregon Territory (1848), which covered present-day Oregon, Washington, Idaho, and parts of Montana and Wyoming.

Idaho's case for inclusion rests on the Columbia River watershed. The Columbia drains Washington, Oregon, and most of Idaho, connecting all three states in a single hydrologic system. Western Idaho shares the geography, ecology, and cultural character of eastern Oregon and Washington. Idaho's exclusion from some definitions comes down to the Pacific coast: it is the only state commonly called Pacific Northwest that has no ocean shoreline.

Quick Answers

What states are in the Pacific Northwest?
Washington and Oregon are in every definition of the Pacific Northwest. Idaho is in most definitions, giving the standard 3-state answer. Western Montana and far northern California appear in some geographic and ecological definitions. No federal agency defines the Pacific Northwest with the same boundary — the Forest Service uses 2 states, the EPA uses 4.
How many states are in the Pacific Northwest?
Two states — Washington and Oregon — are in every definition. Three states — Washington, Oregon, and Idaho — is the most common answer used by Wikipedia, WorldAtlas, and most travel and media organizations. The number ranges from 2 (U.S. Forest Service definition) to 4 (EPA Region 10, which adds Alaska) depending on the source.
Is Idaho in the Pacific Northwest?
Yes, in most definitions. Idaho is included by EPA Region 10, Wikipedia, WorldAtlas, and most reference sources as part of the Pacific Northwest. It is excluded from the U.S. Forest Service's Pacific Northwest Region (Region 6), which covers only Washington and Oregon. Idaho has no Pacific coastline, which is the most common reason for its exclusion from narrower definitions.
Is Montana in the Pacific Northwest?
Western Montana — including Missoula, Kalispell, and Glacier National Park — is sometimes included in geographic and ecological definitions of the Pacific Northwest. Eastern Montana is Great Plains and is not Pacific Northwest by any definition. No federal agency places any part of Montana in the Pacific Northwest.
Is California in the Pacific Northwest?
Far northern California — roughly north of Redding — shares the temperate rainforest ecology of southern Oregon and is occasionally included in geographic definitions of the Pacific Northwest. No federal agency and no major reference source includes California in the Pacific Northwest. Most definitions stop at the Oregon-California border.
What is the largest city in the Pacific Northwest?
Seattle, Washington is the largest city in the Pacific Northwest with a metropolitan area population of approximately 4 million. Portland, Oregon is the second largest at approximately 2.5 million. Boise, Idaho is the largest city in the third core Pacific Northwest state, with a metro population of approximately 800,000.

Methodology

Pacific Northwest classification is based on cross-referencing five sources: U.S. Forest Service Region 6, EPA Region 10, U.S. Census Bureau Pacific division, Wikipedia, and WorldAtlas. States are classified as Always (appear in every source), Usually (appear in most sources), or Sometimes (appear in geographic or ecological definitions only). No single federal authority defines the Pacific Northwest — this comparison makes the disagreement explicit.

Sources

Information is cross-referenced with official state archives.
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