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).
From 1911, when the Sproul Road Act was enacted to 1987, all state highways in Pennsylvania were designated as legislative routes. Some of these also had Traffic Route designations. Major routes received three- or four-digit numbers, while minor routes were assigned five-digit numbers where the first two digits indicated the county, ordered alphabetically from Adams (1) to York (66).