Washington State Route 520

State Route 520
Map of Seattle and the Eastside, with SR 520 highlighted in red
Route information
Auxiliary route of I-5
Maintained by WSDOT
Length	12.82 mi[1] (20.63 km)
Existed	1964[2]–present
Major junctions
West end	I-5 in Seattle
Major intersections	I-405 in Bellevue
East end	SR 202 in Redmond
Location
Country	United States
State	Washington
County	King
Highway system
State highways in Washington Interstate US State Scenic Pre-1964 1964 renumbering Former
← SR 519 → SR 522

State Route 520 (SR 520) is a state highway and freeway in the Seattle metropolitan area, part of the U.S. state of Washington. It runs 13 miles (21 km) from Seattle in the west to Redmond in the east. The freeway connects Seattle to the Eastside region of King County via the Evergreen Point Floating Bridge on Lake Washington. SR 520 intersects several state highways, including Interstate 5 (I-5) in Seattle, I-405 in Bellevue, and SR 202 in Redmond.

The original floating bridge was opened in 1963 as a replacement for the cross-lake ferry system that had operated since the late 19th century. In 1964, SR 520 was designated as a freeway connecting I-5 to I-405. An extension to Redmond was proposed later in the decade. In the 1970s and 1980s, sections of the freeway between Bellevue and Redmond were opened to traffic, replacing the temporary designation of SR 920.

Since the 1990s, SR 520 has been expanded with high-occupancy vehicle lanes (HOV lanes) and new interchanges to serve the Overlake area. In 2016, the original Evergreen Point Floating Bridge was replaced by a wider bridge, as part of a multibillion-dollar expansion program that is scheduled to be completed in the 2020s. The program also includes the construction of new bus infrastructure at Montlake and on the Eastside, as well as a bicycle and pedestrian path along most of the highway's length.