The SR 500 corridor was added to the state highway system in 1937 as Secondary State Highway 8A (SSH 8), a spur of
Primary State Highway 8 (PSH 8) that ran from Vancouver to Camas via Orchards. The highway traveled along Fourth Plain Boulevard in eastern Vancouver, which was built by the
Hudson's Bay Company in the 1820s and named for the Fourth Plain region. A series of country roads connecting the eastern outskirts of Fourth Plain with Camas were built by the 1920s to serve farmers, miners, and the military on the way to
Camp Bonneville. The SR 500 designation replaced SSH 8A in the
1964 state highway renumbering and initially traveled through Vancouver on Fourth Plain Boulevard. The entire highway within Vancouver
city limits, a distance of , was widened to four lanes in 1965 at a cost of $258,000 due to increased traffic from eastern Vancouver. A section between Andresen Road and 112th Avenue, including the interchange with I-205, opened in December 1976. A section from St. Johns Road to Andresen Road was opened in November 1983 and was followed by an extension west to I-5 in 1984. The county government requested that SR 500 be designated the
Henry M. Jackson Parkway in honor of the late Washington senator, but were denied by
WSDOT. A high traffic volume contributed to a high rate of
rear-end collisions and other vehicle accidents, averaging three injuries per week, leading to SR 500 being named the state's second most dangerous highway in 2002. A direct onramp from westbound Fourth Plain Boulevard to eastbound SR 500 near I-205 was constructed in the late 1990s. Replacements for all four of the remaining intersections on SR 500 west of Orchards were proposed unsuccessfully in several state budgets at the turn of the century. A single point urban interchange at Thurston Way near the Vancouver Mall was prioritized and used to test a
design–build contract system, which was expected to save a year of planning and bidding time but cost $3 million more, and was completed in October 2002. On the east side of the mall and the I-205 interchange, the six-lane expressway's sole intersection at Gher Road and 112th Avenue was replaced with an interchange in October 2004, costing $26.5 million and funded by the
Nickel Program gas tax. The state government also expanded a section of SR 500 between Andresen Road and SR 503 to six lanes as part of the project. The expressway formerly ended east of the Gher Road junction at an intersection with SR 503 on 117th Avenue, with SR 500 turning east onto Fourth Plain Boulevard towards Camas. The Clark County government opened a parallel east–west expressway, the Padden Parkway, in stages between 1993 and 2003. SR 500 was re-aligned onto a section of Padden Parkway and Northeast 162nd Avenue in February 2005 by an action of the
Washington State Transportation Commission, allowing Fourth Plain Boulevard to be transferred to county and city control. Design work on the remaining interchange projects was halted in 2002, but resumed with new funding approved by the state legislature in 2006. A
diamond interchange at St. Johns Boulevard was completed in September 2012, costing $48 million and eliminating one of the most collision-prone areas of SR 500. A set of direct ramps to northbound I-5 from SR 500 were planned to be built as part of the
Columbia River Crossing project until it was dropped from the project in 2010. The final pair of intersections on the expressway portion of SR 500, at Falk Road and Stapleton Road, were the site of nearly 400 traffic incidents from 2012 to 2017—mostly rear-end collisions. The two intersections were reconfigured into
right-in/right-out junctions with a continuous median barrier, costing $1 million and completed in October 2018. The Falk Road pedestrian overpass was retained, The eastern terminus of SR 500 at SR 14 in Camas was converted into a
dumbbell interchange with
roundabouts in 2012 as part of a freeway extension through the area. Long-range plans proposed by WSDOT and the county government call for the remainder of SR 500 between Orchards and Camas to be upgraded to freeway standards. These plans have not been funded by the state government. ==Major intersections==