Washington State Ferries (WSF) is a government agency that operates automobile and passenger ferry service in the U.S. state of Washington as part of the Washington State Department of Transportation. It runs 10 routes serving 20 terminals located around Puget Sound and in the San Juan Islands, designated as part of the state highway system. The agency maintains the largest fleet of ferries in the United States at 24 vessels, carrying 23 million passengers in 2014. , it was the largest ferry operator in the United States, and the fourth-largest ferry system in the world.