It depends on which sub-species you want to go for. If you are looking at your best bet at bagging a bird, with out a doubt you need to head to Eastern WA - Kettle falls down to Spokane - all Merriams but a lot of em'

Along the Tucannon river outside Dayton there are large amounts of Rio's

Easterns are the tough nut to crack in WA... You'll hear a lot about Johnson Creek and other areas but the birds are few and the hunters are many.

For the most up to date turkey hunting information in Washington check out

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Tacoma NWTF
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If you have any questions, feel free to contact me. Good luck this year!