Tracing Washington State regulatory history involves a similar process as explained under Federal Regulatory History. See our guide to Administrative Law: Online Resources for links to access the Washington Administrative Code and the Washington State Register online.
Start with your citation to the Washington Administrative Code (WAC).
Once you have found your WAC regulation, look at the bottom of the text. You'll see a citation to the Revised Code of Washington (RCW) granting authority for the regulation.
In this same section, you will also find a citation to the Washington State Register (WSR) where these regulations are published prior to being codified in the WAC. The WSR will contain historical information regarding the regulation, including providing a statement of purpose for the proposed rules. You may also find other documents preproposal or interpretive statements.