What pass do I need?

For Washington state you really only need 2 annual passes and you can virtually get in/ park at most trailheads.  (Some city or county owned parks may have a fee not covered by these state and national passes)

America the beautiful is 80$/ yr for an annual pass and it gets one vehicle entrance and parking at any National Park or National Forest among other National lands. If you have a 4th grader you get a FREE pass! There is senior passes as well as a lifetime FREE access pass for individuals with a permanent disability. 

https://www.nps.gov/planyourvisit/passes.htm

Discover Pass covers all State operated parks. It cost  30$ annually. Some libraries even have a borrow system for a pass! The state also has a FREE 5 year pass for individuals with a disability. 

https://www.discoverpass.wa.gov/31/About-the-Pass