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. A smaller change was the removal and truncating of many
U.S. Routes in favor of the
Interstate Highways (designated in 1959), and the renumbering of State Routes that conflicted with Interstate numbers. Some U.S. Routes that were officially removed continued to be signed until the replacement Interstates were completed.