Interstate 605 (Washington)

Interstate 605
Proposed 1998 corridor of I-605 highlighted in red
Route information
Auxiliary route of I-5
Status	Never built
NHS	Entire route
Location
Country	United States
State	Washington
Highway system
Interstate Highway System Main Auxiliary Suffixed Business Future State highways in Washington Interstate US State Scenic Pre-1964 1964 renumbering Former
← SR 603 → SR 702

Interstate 605 (I-605) is the popular moniker given to several proposals for a new auxiliary Interstate Highway bypassing I-5 and I-405 in the U.S. state of Washington. Proposals have been heard from since the 1960s, including highways connecting from I-5 all the way to the Canada–US border, and some just between I-5 and I-90. The Washington State Department of Transportation (WSDOT) has no projects designated I-605 at this time. However, some I-605 proposals have included State Route 18, which has been partially constructed as a freeway.