1964 state highway renumbering (Washington)
It was first signed in January 1964 and codified into the Revised Code of Washington in 1970.The former numbering system of primary and secondary state highways, using lettered suffixes and unnamed branches, created confusion for motorists as the system expanded.[1] The state highway department originally planned for a major highway renumbering in 1957, expanding on the existing primary and secondary system with numbers as high as 59, but serious consideration of a full-scale renumbering began in 1962.[4] The law came in response to confusion experienced by tourists visiting during the 1962 World's Fair, held in Seattle.[8] The new numbering system took effect on January 15, 1964,[9][10] and new signs were posted at a cost of $115,000.