this is what I found and my brother says Klickitat county is the place to research,
if you do a search on google for klickitat county turkey hunting you can find a lot of info for your search. I posted the link to this info I found
The three subspecies of wild turkeys around the state include the Merriam’s, Rio Grande, and Eastern. Currently, the Merriam’s subspecies occupies portions of Ferry, Klickitat, Pend Oreille, Skamania, Stevens, Spokane, Okanogan, Chelan, Kittitas, and Yakima counties.
Rio Grande turkeys can be found in Asotin, Columbia, Garfield, Lincoln, Walla Walla, and Whitman counties.
Confusingly, the Eastern subspecies are found western half of the state in Cowlitz, Grays Harbor, Lewis, Mason, Pacific, Thurston, and Wahkiakum counties.
Of the three subspecies, the toughest to hunt is the Eastern variety on the west side of the state. Not only are Easterns supposed to be more wary, they live in some thick places, with lots of private land surrounding them. And their population numbers are much lower than the Rios and Merriam’s.
Because there are three different subspecies, and because they have good numbers of turkeys in several counties in eastern Washington, hunters are allowed to shoot three turkeys in the spring, with the following restrictions: only two turkeys may be taken in eastern Washington and only one of those may be taken in Chelan, Kittitas, or Yakima counties (combined); only one turkey may be taken in western Washington outside of Klickitat County. Two turkeys may be taken in Klickitat County.
When you look at the spring turkey harvest numbers over the past 16 years you can see there have been some ups and downs but for the most part the annual harvest has been pushing 5,000 birds with a few years bumping over that.
you can read the whole article here https://www.yakimaherald.com/sports/outdoors/phillips-turkey-season-could-be-one-of-the-best/article_1315d78e-3890-11e8-8444-8bcd62a87769.html