The following Washington State Department of Labor & Industries page contains current and future minimum wage rules in the state of Washington. Increases are coming starting January of 2020 and 2021. This page also has resources including an FAQ section and the most recent laws, policies and more information.
Employers with workers who work in certain local jurisdictions may be subject to a higher minimum wage than the state rate.
See this Washington L & I page: https://www.lni.wa.gov/WorkplaceRights/Wages/Minimum/