Each is assigned a four-digit State Route (SR) number in the present Location Referencing System.

[1] The Pennsylvania State Route System was established by the Sproul Road Bill passed in 1911.

Four-digit State Routes are unsigned, except on small white reference markers near physical features such as intersections and bridges, and are unique within each county.

Underneath, there is a larger typeface number identifying the segment of highway being entered.

Segments are typically one half mile long and are usually numbered in multiples of 10 on non-Interstate highways.