The Washington State Department of Agriculture maintains a page on their web site specifically for Apiarists.
On it you will find the laws, general information and a registration form to register your hives.
The association strongly recommends that you register your hives. For 1 to 5 hives it is a nominal cost of $5 per year.
Link: Washington State Department of Agriculture - Apiary
PDF: Apiary Registration Form
A PowerPoint presentation by Patrick Sturgill and Mary Haynes, on attempting to build a Top Bar Hive.
Our Main Source of Information: Phil Chandler, aka The Barefoot Beekeeper found at biobees.com