[4] Eastern Washington is composed of Adams, Asotin, Benton, Chelan, Columbia, Douglas, Ferry, Franklin, Garfield, Grant, Kittitas, Klickitat, Lincoln, Okanogan, Pend Oreille, Spokane, Stevens, Walla Walla, Whitman, and Yakima counties.

Some definitions also include part of Skamania County that lies east of the ridge line of the Cascade Mountains.

The east and west do still have some climatic traits in common, though: more rainfall in winter than summer, a lack of severe storms, and milder temperature ranges than more inland locations.

As of the 2020 census, Eastern Washington was home to 1,667,593 of the state's total 7,705,281 residents, making its population comparable to that of West Virginia.

[14] Proposed names for the new state have included Lincoln, Columbia, Liberty,[15] or simply Eastern Washington.