SR 16 was created during the 1964 state highway renumbering as the successor to Primary State Highway 14 (PSH 14). PSH 14, which had itself been the successor to State Road 14, traveled northeast from Shelton to Gorst and south to Gig Harbor. PSH 14 was extended over the Tacoma Narrows in 1939 on the unfinished Tacoma Narrows Bridge, which would later collapse months after opening in 1940, into Tacoma over Secondary State Highway 14C (SSH 14C). 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. Future 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, scheduled for completion by 2022.