successor to both SSH 1D and SSH 1I. The highway was extended south and east from Highway 99 to the newly-completed I-5 in February 1965, using 164th Street NE until a new freeway could be constructed. The highway was truncated from Anacortes to its present terminus south of Coupeville after SR 20 was extended across the state on the North Cascades Highway in 1973. SR 525 was re-aligned onto a two-lane freeway between SR 99 and the Swamp Creek in the 1980s, extending the route to I-405. The Swamp Creek Interchange itself was completed in November 1984. WSF ferry routes were added to its respective state highways in 1994, eliminating one of two gaps along the route of SR 525, the other being a concurrency with SR 99 that was replaced by a partial cloverleaf interchange in 2000 during the widening of the freeway segment in Lynnwood. A spur route, located completely in Mukilteo, was added to SR 525 in 2001 along the route of the four-lane Paine Field Boulevard, connecting the main highway to SR 526. The Mukilteo ferry terminal, originally completed in 1957, was replaced by a new facility that opened on December 29, 2020. The new terminal, which includes a waiting area, longer car queues, and a transit center, cost $187 million to construct. Major intersections Spur route SR 525 has a spur route on Paine Field Boulevard in Mukilteo that connects the northbound lanes of the Mukilteo Speedway to SR 526 eastbound towards Everett and the local Boeing factory. Paine Field Boulevard was built in 1999 and signed as SR 525 Spur in 2001, subsequently being widened and improved in 2003 by WSDOT. A proposal to extend Paine Field Boulevard through Japanese Gulch and create a bypass of the Mukilteo ferry terminal has been a part of the city's transportation plan since 2001, but has not been built. WSDOT estimated, during its annual AADT survey, that 21,000 vehicles used the highway in 2012. References External links Highways of Washington State Whidbey Island Scenic Byway 525 525 Transportation in Snohomish County, Washington Transportation in Island County, Washington