In 1963 and 1964, the California Division of Highways implemented a major renumbering of its state highways. The majority of sign routes - those marked for the public - kept their numbers; the main changes were to the legislative routes, which had their numbers changed to match the sign routes. A large number of formerly unsigned routes received sign numbers corresponding to their new legislative numbers.

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, 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.