1964 state highway renumbering (Washington)

In 1963, a law was passed authorizing a new numbering for sign routes. In 1970 the legislative definitions were changed to use the sign route numbers but renamed state routes. Those definitions, with amendments, are still in use today.

In 1964, the Washington State Department of Transportation (WSDOT) created a new numbering system, the State Route system, out of the existing Primary State Highways (PSH) and Secondary State Highways (SSH) system. The new system, called State Routes or Signed Routes (SR), consolidated and created a more organized and systematic method of numbering the highways within the state. The system also introduced accordance with the new Interstate Highway system, with the creation of Interstate 5 within the state.