 The Bothell–Everett portion of the highway was paved with concrete in 1916, following a bond issue for improved roads approved by Snohomish County voters the year prior.The Pacific Highway, later numbered to State Road 1 in 1923 and part of U.S. Route 99 in 1926, remained on the Bothell route until the completion of a straighter north–south highway to the west in 1927.The Bothell–Everett highway was incorporated into part of SSH 2A in 1937, forming a continuous route between Renton and Everett via the Eastside.