rebuilt as a steel structure in 1915. The King County government followed suit with several state-funded paving projects on the eastern highway in the 1910s and 1920s. By the mid-1920s, the paved Snoqualmie Valley highway extended south from Monroe to the King–Snohomish county line north of Duvall, while the remainder was described as an improved road with varying quality. The road was incorporated into the state highway system in 1937 as Secondary State Highway 15B (SSH 15B), connecting Primary State Highway 15 (PSH 15) in Monroe to PSH 2 and U.S. Route 10 (US 10) in Fall City. The state legislature approved funds to pave the entire highway in 1937 and oiling of the road from Carnation to Duvall was completed two years later. The final paving projects were approved in 1945 and completed over the following three years alongside the replacement of sixteen wooden bridges. The state also straightened sections of SSH 15B near Fall City in the 1940s and through the Tualco Valley south of Monroe in the 1950s. The Lewis Street Bridge over the Skykomish River in Monroe was replaced by the state in 1957 at a cost of $526,000. The state legislature reformed the numbering system for state highways in 1964, re-designating SSH 15B as State Route 203. The branch railroad running parallel to the highway was abandoned in the 1970s and later converted into the Snoqualmie Valley Trail. The Tolt River Bridge in Carnation was replaced with a new span in 1977. The Snoqualmie Valley area was proposed in the late 1990s and early 2000s as the corridor for a proposed outer bypass of the Seattle metropolitan area, popularly named Interstate 605. The state legislature commissioned a study in 1998 to determine the feasibility of constructing the freeway, which would have traveled from southern King County to Everett via SR 18 and the SR 203 corridor in the Snoqualmie Valley. The study determined that through-travelers would have only saved five minutes over peak travel times and the legislature shelved the plan. A second study commissioned in 2003 determined that a highway built north of Snoqualmie would not be economically feasible and would fail to sufficiently benefit freight interests to justify its multibillion-dollar cost. In the 2000s, WSDOT began a series of construction projects on sections of the SR 203 corridor that aimed to improve traffic congestion and increase road safety. A roundabout was constructed in