King County Metro, officially the King County Department of Transportation Metro Transit Division or Metro for short, is the public transit authority of King County, Washington, a division of the King County Department of Transportation. It began operations on January 1, 1973, but can trace its roots to Seattle Transit, founded in 1939, and Overlake Transit Service, founded in 1927. As of 2015, it operated 1,882 buses on 215 routes. Its annual ridership in 2012 was over 114 million making it the 8th largest agency in the nation. Metro employs 2,716 full- and part-time operators (year-end 2012).