Pennsylvania State Route

Pennsylvania State Route System
State route markers in Pennsylvania.
System information
Notes:	All routes are assigned State Route (SR X) numbers, usually corresponding to the signed numbers. State Routes are generally state-maintained.
Highway names
State:	Pennsylvania Route X (PA X)
Special Routes:	Pennsylvania Route X Alternate (PA X Alt.); Pennsylvania Route X Alternate Truck (PA X Alt. Truck); Pennsylvania Route X Business (PA X Bus.); Pennsylvania Route X Bypass (PA X Byp.); Pennsylvania Route X Truck (PA X Truck)
Quadrant Routes:	State Route X (SR X)
System links
Pennsylvania State Route System Interstate US State Scenic Byways Legislative

The Pennsylvania Department of Transportation (PennDOT) is responsible for the establishment and classification of a state highway network which includes interstate highways, U.S. highways, and state routes. U.S. and Interstate highways are classified as state routes in Pennsylvania. The Commonwealth of Pennsylvania established the Location Referencing System (LRS) in 1987, which registers all numbered routes in Pennsylvania as SR-X. A state route would be SR 39, a US Route would be SR 22, and an interstate route would be SR 80. However, routes which are numbered between 0000 and 0999 are classified as Traffic Routes, which are abbreviated as PA 39, US 22, and I-80, instead. There are also four-digit numbers for various "state roads" over which PennDOT has jurisdiction, but those numbers are not displayed on the roads, except in rural areas, where they are posted with index-card-sized small signs. In urban areas, these numbers are somewhat less prominently posted, and these streets are known by the names on the street signs.

In 1911, when the Sproul Road Bill was passed, a large number of Legislative Routes (LR) were assigned. These were the primary internal numbering until the present Location Referencing System was adopted in 1987. See also list of Legislative Routes in Pennsylvania.

Signed Traffic Route numbers from 1 to 12 were first assigned in 1924 to several of the national auto trails:

Italics denote former routes.

Soon more numbers were assigned, including three-digit numbers for branches, like Pennsylvania Route 272 from Pennsylvania Route 72. The United States Numbered Highways were assigned in late 1926, and in 1928 State Routes concurrent with U.S. Routes were removed, while those that conflicted with U.S. Routes were assigned new numbers. The establishment of the Interstate Highway System in 1959 resulted in a small renumbering in 1961.