State Route 522 (SR 522) connects Seattle to its northeastern suburbs. Its southern origin is at Interstate 5 at the north end of the Roosevelt neighborhood in north Seattle, where it is a city arterial, Lake City Way N.E. Upon crossing the Seattle city limits into Lake Forest Park, its name changes to Bothell Way N.E. It continues through Kenmore and into Bothell, where part of it is designated Woodinville Drive. East of downtown Bothell, SR 522 becomes a freeway as the first segment of the Bothell-Monroe Highway. It continues through Woodinville to an at-grade intersection with Paradise Lake Road. From there, it continues east as a two-lane freeway into unincorporated Snohomish County to Monroe, where it ends at the junction with U.S. Route 2. It is about 25 miles (40 km) long in total.

Once called the Red Brick Road, SR 522 originally connected Downtown Seattle to the towns of Lake City, Lake Forest Park, Kenmore, Bothell, Redmond, Falls City and points east. From 1926 to the late 1930s, U.S. Route 99 followed the present day SR 522 from Seattle to Woodinville. Rebuilt and expanded after World War II, it remained a connector from downtown Seattle through to Redmond until the construction of Interstate 5, when its origination point moved several miles north along that freeway into the Roosevelt neighborhood of Seattle.

After 1970, the easternmost portion of SR 522 from Bothell to Woodinville, Redmond, and North Bend was renumbered as State Route 202, and the portion of what had been SR 202 between Bothell and Monroe was renumbered as SR 522. A highly-utilized bypass to reach Stevens Pass, 1,780 accidents, 1,359 injuries, and 47 deaths in 15 years resulted in the highway being included in the September 1995 Reader's Digest article "America's Most Dangerous Highways." The route has also been featured in a Dateline NBC story and a 2007 Forbes Magazine article for similar reasons.

Highway 522 east of Woodinville was historically mainly an undivided, rural two lane highway serving farming communities to the east. Rapid suburbanization of Snohomish County and dramatic increases of population in Snohomish County suburbs like the city of Monroe and unincorporated Maltby have led to overcapacity and dangerous highway conditions.

The Highway 522 Corridor Improvements plan created by the Washington State Department of Transportation seeks to address these issues. Some of the projects listed below are fully funded/constructed and some have partial or no funding allocated yet.

A highway interchange with entrance and exit on and off ramps was constructed and completed in August 2006 to replace the signalized intersection that existed before.

The existing two lane undivided highway will be expanded to four lanes with a median to separate opposing lanes of traffic and a new bridge will be built across the Snohomish River. This project is fully funded by the 2003 Nickel Gas Tax passed by the Washington State Legislature and is scheduled to be constructed from spring 2009 to late 2014.