High Quality Content by WIKIPEDIA articles! State Route 531 (SR 531) is a short Washington state highway in Snohomish County. It extends east 9.88 miles (15.90 km), from Wenberg County Park in the community of Lake Goodwin, to SR 9 in southeast Arlington. SR 531 intersects Interstate 5 (I-5), and passes the Arlington Airport. The route connects I-5 to SR 9, Smokey Point, and Wenberg County Park. The Washington State Legislature approved SR 531`s current route in 1991. Since then, construction projects, arranged by the Washington State Department of Transportation (WSDOT), have turned this small road into an arterial street. Even though the Washington State Legislature and WSDOT approved SR 531 in 1991, they erected no signs until April 1, 1992, when the law creating the road took effect.