SR 16 has been expanded into a freeway in stages beginning with the original Nalley Valley Viaduct in Tacoma in 1971, and ending with the opening of an interchange near Port Orchard in 2009.

Later improvements to the corridor include the installation of high-occupancy vehicle lanes that connect to I-5 and the rest of the freeway network in Pierce County, which were completed in 2019.

[11] The freeway bypasses Purdy and Peninsula High School to the east before intersecting SR 302 Spur and entering Kitsap County.

[12] SR 16 passes the community of Burley and intersects its main access highway, Burley-Olalla Road, in an interchange before entering the city of Port Orchard.

State Road 14 traveled north from Shelton to Gorst and south into Gig Harbor as the primary connector between the Olympic and Kitsap peninsulas.

[23] State Road 14 was re-designated in 1937 as PSH 14 and included a secondary highway named SSH 14C that traveled from Gig Harbor to the Tacoma Narrows, site of an under-construction suspension bridge to open in 1940.

[27] After the collapse of the original bridge on November 7, 1940,[28] PSH 14 was truncated to Gig Harbor and traffic was redirected to a ferry landing in Manchester.

[2][32] WSDOT began converting the SR 16 corridor to a controlled-access freeway with the construction of the Nalley Valley Viaduct in 1969, designed with tetrapod columns at a cost of $3.67 million.

[42] Beginning in the early 2000s, frontage roads and the Scott Pierson Trail were built along the freeway and sound walls were erected near residential areas in Tacoma.

[51] The northern terminus of SR 16 in Gorst is a major traffic bottleneck and forms a gap between the two main freeways on the Kitsap Peninsula.

A rebuilt interchange, estimated to cost around $500 million, has been sought to improve access to Bremerton National Airport and local military installations.

[26] The Northern Pacific Railway planned to build a trestle bridge over the Narrows to connect its western terminus in Tacoma to the proposed Puget Sound Naval Shipyard in Port Orchard.

[26] The Washington State Legislature, after extensive lobbying by local auto groups and businesses, authorized the construction of a road bridge over the Narrows in February 1929.

The 2,800-foot-long (850 m) bridge, christened the name "Galloping Gertie" by its construction workers, cost $6.4 million to build and became the third longest suspension span in the world after its completion.

[31][59][60] The increased traffic prompted the Washington State Legislature to approve the construction of a tolled eastbound bridge in 1999, to be finished during the early 2000s.