From Lynnwood, the highway serves Mukilteo and becomes the terminus of SR 526 before taking its ferry route to Clinton on Whidbey Island.SR 525 begins at the Swamp Creek Interchange with I-5, also serving as the northern terminus of I-405, located in Lynnwood in southern Snohomish County.The ferry was later taken over by the Puget Sound Navigation Company, later sold to the state government in 1951 to form the WSF.[23] SSH 1D traveled 54.73 miles (88.08 km) on Whidbey and Fidalgo islands from the Clinton ferry dock to an intersection with the Anacortes branch of PSH 1 at Sharps Corner.[32] The new terminal, which includes a waiting area, longer car queues, and a transit center, cost $187 million to construct.[33] In April 2024, Mukilteo mayor Joe Marine floated the idea of renaming Mukilteo Speedway during a work session with the city council to better reflect the city's history; it was axed two months later after it received overwhelming opposition among participants in an online survey and a Facebook post soliciting feedback.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.
The Swamp Creek Interchange in
Lynnwood
, the southern terminus of SR 525 and the northern terminus of
I-405
, viewed from above in 1967. The overpass in the distance is 164th St. SW, where SR 525 was designated at that time.