SR 204 begins in Cavalero Corner at an interchange with US 2 at the east end of the Hewitt Avenue Trestle, which crosses Ebey Island and connects the highway to Everett.

[2][3] The highway ascends from the Snohomish River estuary and runs northeasterly along the edge of several suburban neighborhoods before entering the city of Lake Stevens.

After crossing under a set of transmission lines near Market Place, the highway widens to four lanes and enters the Frontier Village commercial district.

[7][8] The original route of the Pacific Highway between Everett and the rest of northwestern Washington ran across Ebey Island and turned north onto Sunnyside Boulevard at Cavalero Corner before continuing into Marysville.

[9] Vernon Road, constructed in the 1910s and paved in 1916,[10] branched off from Sunnyside Boulevard at the bottom of Cavalero Hill and traveled northeasterly along the shore of Lake Stevens to the settlement of Hartford.

[11] The Pacific Highway was moved in the late 1920s to a more direct route traversing set of new bridges across the Snohomish River estuary,[9] while the Ebey Island road itself was replaced by the completed Hewitt Avenue Trestle in 1936.

[22] In early 2019, WSDOT announced that it would re-examine an earlier concept to use roundabouts to manage the intersection at a lower cost compared to the chosen interchange option.