as Primary State Highway 1 (PSH 1). During the creation of the primary and secondary state highways in 1937, the highway between Tacoma and Federal Way was designated as SSH 1V and the highway between Des Moines and Seattle was designated as SSH 1K. SSH 1V traveled north from PSH 1 in Tacoma through the Port of Tacoma on the 11th Street Bridge and the Blair Bridge, opened in 1913 and 1953 respectively, to Federal Way, ending at an intersection with SSH 1K. SSH 1K traveled south from PSH 1 at the First Avenue South Bridge in Seattle through Burien and east through Des Moines to PSH 1 in Midway. The two highways were combined during the 1964 highway renumbering to become SR 509 and was codified into law in 1970. The Des Moines–Burien Freeway was approved by the Washington State Highway Commission in 1966, as part of a longer freeway corridor connecting the ports of Tacoma and Seattle. An earlier proposal from 1967 to connect the north end of SR 509 to I-5 via an expressway on Michigan Street and a new crossing of the Duwamish River was studied but was never built. SR 509 was realigned onto the newly constructed Burien Freeway in November 1968, extending from Seattle to SeaTac. The highway was originally routed through Saltwater State Park on Marine View Drive until 1991, when SR 509 was moved to two concurrencies with SR 99 in Federal Way and SR 516 in Des Moines. The freeway was planned to be extended south to SR 516 in the 1970s after a right-of-way was acquired by WSDOT before the project was canceled due to public opposition. The King County Department of Public Works recommended extending SR 509 southeast from South 188th Street to I-5 in 1988, with construction planned to begin in 1999 at an estimated cost of $252 million in 1996, raised to $1.4 billion a decade later. A freeway bypass of the Port of Tacoma for SR 509 was proposed in 1990 as a supplement to the newly completed I-705 and funded with a $180 million grant from the Federal Highway Administration approved the following year. Construction began in early 1994 amid controversy over the freeway's effects on the redevelopment of the Thea Foss Waterway. The first section of the new freeway opened in August 1995, while the cable-stayed bridge over the Thea Foss Waterway and single-point