Puget Sound Regional Council major cities are Seattle, Bellevue in King County, Tacoma in Pierce County, Everett in Snohomish County, and Bremerton in Kitsap County. The region's population was estimated to be over 3.8 million as of April 2014. In 1956 the four counties of the Puget Sound region established the Puget Sound Regional Planning Conference, which changed its name to the Puget Sound Governmental Conference (PSGC) in 1958. It launched the Puget Sound Regional Transportation Study (PSRTS) in 1962 with support from the Washington State Highway Commission, the U.S. Bureau of Public Roads (predecessor of the Federal Highway Administration), and the U.S. Department
Puget Sound the ice sheets had retreated. Because the rate of rebound was not synchronous with the post-ice age rise in sea levels, the bed of what is Puget Sound, filled alternately with fresh and with sea water. The upper level of the lake-sediment Lawton Clay now lies about above sea level. The Puget Sound system consists of four deep basins connected by shallower sills. The four basins are Hood Canal, west of the Kitsap Peninsula, Whidbey Basin, east of Whidbey Island, South Sound, south of the Tacoma Narrows, and the Main Basin, which is further subdivided into Admiralty Inlet and the