Washington operates its own state-based marketplace, Washington Healthplanfinder, rather than using HealthCare.gov. Residents shop for plans and apply for subsidies directly through the state exchange.
Washington expanded Medicaid under the ACA, so adults earning up to 138% of the federal poverty level generally qualify for Apple Health, the state's Medicaid program, instead of needing a subsidized marketplace plan.
Washington has also experimented with public option style plans, called Cascade Care plans, sold by private insurers but built to state-set standards for cost sharing, so it's worth comparing those alongside standard marketplace plans. Shoppers on the east side of the state versus the Seattle metro area should confirm network coverage, since provider access can differ across Washington's geography.