Old 99 follows State Street thru Marysville towards Smokey Point and Jct WA 530. Outside the city limits, the name changes to Smokey Point Blvd. At SR 530, old 99 turns left and heads west along WA 530 to I-5. Crossing I-5, WA 530 ends and the old highway continues with the name Pioneer Highway. The 1919 vintage thru truss on this route across the Stillaguamish River was replaced by a new bridge in the 1980s. Stanwood used to be two separate cities, Stanwood and East Stanwood, The original Pacific Highway headed west from East Stanwood to Stanwood, then north to Conway. A realignment of 99 circa 1931 avoided (west) Stanwood. A more major realignment around 1933-34 avoided East Stanwood-Stanwood altogether. Starting between Smokey Point and WA 530, a more direct route following today's I-5 was built. Although 2 lanes when first opened, this route included a 4 lane 3 span thru truss bridge across the Stillaguamish. Back at Marysville, a 4 lane expressway was built from the south end of town to the south end of Smokey Point in the mid 1950s. This expressway was upgraded to 6 lane I-5 freeway around 1970. Smokey Point itself was not bypassed until around 1959 with an expressway. The 1930s highway from north of Smokey Point to Conway was paralleled in the mid 1950s with a one way 2 lane expressway. This 2 lane expressway was continued north from Conway to the south end of Mount Vernon. Interchanges were added to US 99/I-5 at Smokey Point and Jct WA 530 in the mid 1960s. I-5 was upgraded to 6 lane freeway to the south end of Mount Vernon in the early 1970s. Most of the 1930s US 99 from WA 530 to Conway is now a frontage road. The 1933 Stillaguamish River Bridge now carries 3 lanes of southbound I-5.