 In 2011, WSDOT calculated that the busiest section of SR 96 was its western terminus at I-5, serving 43,000 vehicles, while the least busy section is its eastern terminus at SR 9, serving 11,000 vehicles.Seattle Hill Road and 131st Street have existed since 1885 on their present route as part of a wagon road constructed by Snohomish County connecting Snohomish to Seattle.The highway from Seattle Hill through Mill Creek was completed by the late 1950s and paved in the early 1960s by the county.