ADA Hiking Trails throughout Washington: Washington Trail Association has put together a resource that allows you to find barrier-free ADA hiking trails throughout the state. (https://www.wta.org/go-outside/seasonal-hikes/summer-destinations/ada-accessible-hikes)
Rolling Washington (Wheelchair-friendly trails): Rolling Washington provides information on wheelchair-accessible trails throughout five regions of Washington. (https://rollingwashington.org/)