From the 1911 passage of the Sproul Road Bill to the 1987 adoption of the Location Referencing System, all state highways in the U.S. state of Pennsylvania were defined as legislative routes, while some were also posted as Traffic Routes. Major routes were assigned three- or four-digit numbers, while minor routes were given five-digit numbers in which the first two digits represented the county, in alphabetical order from 1 (Adams) to 66 (York).
Between 1911 and 1987, all Pennsylvania state highways were classified as legislative routes. Some also had Traffic Route designations. Major routes were assigned three- or four-digit numbers, whereas minor routes received five-digit numbers with the first two digits representing the county in alphabetical order from Adams (1) to York (66).