 State Route 308 ( SR 308 ) is a 3 @.@ 42 @-@ mile @-@ long ( 5 @.@ 50 km ) state highway in the U.S. state of Washington , serving the community of Keyport in Kitsap County . The highway travels generally east from an interchange with SR 3 east of Naval Base Kitsap at Bangor to the main entrance of the Naval Undersea Warfare Center in Keyport . SR 308 was codified as the Keyport branch of State Road 21 in 1929 and continued as the Keyport branch of Primary State Highway 21 ( PSH 21 ) in 1937 . During the 1964 highway renumbering , the branch became a section of SR 303 , which ran from Bremerton to Bangor and had a spur route serving Keyport . SR 308 was established in 1971 along the old route of SR 303 Spur and was extended in 1991 to the SR 3 freeway after SR 303 was re @-@ routed onto a new freeway in Silverdale . 
