During the creation of the primary and secondary state highway system in 1937, the paved State Roads 14 and 21 kept their numerical designations and became PSH 14 and PSH 21, respectively. PSH 21 was extended southwest from Bremerton on the former Navy Yard Highway to Gorst, while PSH 14 turned south at Gorst and headed towards Tacoma. A branch of PSH 14, named SSH 14A, was designated on a gravel road that connected the main highway at Belfair to US 101 in Shelton. In 1955, PSH 21 was extended southwest along PSH 14 from Gorst to Union, shortening PSH 14 to its current route as SR 16.