The WACO Board of Trustees consists of 19 positions: the President, Vice-President, 2nd Vice-President, Secretary/Treasurer, the 2 most recent Past-Presidents, 1 member chosen by their respective affiliate (known as a trustee), and 6 positions as trustees-at-large based on their county category.

1. Population over 1 million - Counties: King
2. Population 400,001 - 1 million - Counties: Clark, Pierce, Snohomish, Spokane
3. Population 100,001 - 400,000 - Counties: Benton, Cowlitz, Grant, Kitsap, Skagit, Thurston, Yakima, Whatcom
4. Population 50,001 - 100,000 - Counties: Chelan, Clallam, Franklin, Grays Harbor, Island, Lewis, Mason, Walla Walla, Whitman 
5. Population 20,000 - 50,000 - Counties: Adams, Asotin, Douglas, Jefferson, Kittitas, Klickitat, Okanogan, Pacific, Stevens
6. Population Under 20,000 - Counties: Columbia, Ferry, Garfield, Lincoln, Pend Oreille, San Juan, Skamania, Wahkiakum