Washington State Parks expect letterboxers to follow the permitting system established for geocachers. In order to place a letterbox on State Parks' property, an individual or organization must obtain a Geocache Placement Permit from State Parks. Any letterbox located on State Parks' property that does not have a permit on file is subject to removal from its location, and after notification of the owner (if known), may be disposed of within 10 days.

Washington State Parks supports and encourages these recreational activities in state parks as long as participants follow the placement guidelines and you have a current permit. The permits are free and easy to fill out. You can find information and a link to permits by following the link provided:
Washington State Parks Activities . Please fill it out and submit it to the park where your property will be located.

Washington State Parks
Official Policy and Permit Application: Good as of June 6, 2006