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The Pennsylvania State Route Numbering System
Early Numbering Systems


The old Pennsylvania Department of Highways and the current Department of Transportation have simultaneously employed various versions of two simultaneous numbering systems. First, state-maintained highways were given legislative numbers in 1911, and these were renumbered according to a new system in the 1980s. These numbers are reference numbers that were and are useful for bookkeeping and documenting the state highways. Second, a visible, more user-friendly system was developed in 1925 (and revamped in 1928 and in later years) for the driving public. This system originally encompassed the signed state routes 1-999, but included the US highway system in 1928 and the Interstate highway system decades later.


The Original 1911 System (Internal Use)

The original system, begun on May 31, 1911 under the Sproul Road Bill, assigned sequential numbers to short segments of state roads, covering numbers as high as the 300s by 1925. These highways and their numbers were found on road maps of the 1911-1925 era with designations such as State Highway No. 244. The numbers became the legislative route (LR) numbers that were used until the SR system was effected in the 1980s. By its last few years, the numbering system had three subsystems:

  1. Sequentially numbered routes · Routes numbered 1, 2, ... to numbers in the low 1000s. These routes were the only ones in existence until 1925, when the signed state routes were established. In 1925, the majority of the signed state routes (which had their own numbering system; see below) followed these sequentially numbered routes. Later on, signed state routes still mainly followed these low-numbered LRs but commonly followed the high-numbered ones or other LRs.
  2. County-based routes · Many five-digit routes were established with numberes decided according to the county. The 67 county names were alphabetized, and Philadelphia County was excluded from the list. The remaining counties were numbered 01 (Adams County) to 66 (York County), and these county codes were used as the first two digits of the five-digit county routes. The remaining three digits were used to distinguish the different five-digit routes within a county.


The New 1925 System (Public Use)

The 1925 system established the signed routes numbered especially for travellers. The system assigned one-digit numbers and a few two-digit numbers to major highways ("auto trails") across the state, with even numbers assigned to north-south routes and odd numbers assigned to east-west routes. The route numbers increased from east to west (2 near New Jersey, 8 near Ohio) and from south to north (1 near Maryland, 9 near Lake Erie). The 1911 LR numbers remained as an internal referencing system. The 1925 system was envisioned in 1924, but probably was not noted on maps until the following year. The system began by numbering nine auto trails that were far better known by name:


Route Auto Trail Remarks
Lincoln Highway West Virginia to New Jersey via Pittsburgh and Philadelphia; now mainly US 30 west of Philadelphia and US 1 to the east.
Lackawanna Trail New York to Philadelphia via Scranton and Easton; now mainly US 1 north of Scranton and PA 611 to the south
William Penn Highway West Virginia to New Jersey via Pittsburgh, Harrisburg, and Allentown; now US 22, US 322, US 422, US 222, and US 22 from west to east.
Susquehanna Trail New York to Maryland via Williamsport, Harrisburg, and York; now mainly US 15, I-180, US 11/US 15, and I-83 from north to south.
Lakes-to-Sea Highway Erie to Philadelphia via Meadville and Harrisburg; now mainly PA 97, US 322, and PA 3 from northwest to southeast.
Roosevelt Highway Waterford to New York via Mansfield and Scranton; now mainly US 6.
Chicago-Buffalo Highway, Yellowstone Trail Via Erie; now US 20
National Old Trails Road
National Pike
Maryland to West Virginia via Uniontown and Washington; now US 40..
Baltimore Pike Portland to Maryland via Bethlehem and Philadelphia; now PA 512, PA 378, PA 309, and US 1 from north to south.


Other auto trails were also numbered shortly thereafter. By 1926, the following auto trails were included.


6 Old Monument Trail Bradford to Grantsville via Dubois and Johnstown; now mainly US 219.
8 William Flinn Highway Erie to Morgantown via Pittsburgh, now mainly US 19 and PA 8.
13 Highway from Chambersburg to Philadelphia Via Harrisburg; now mainly US 11, US 322, and US 422 from west to east.
19 Highway from Scranton to Lewistown Via Sunbury; now mainly US 11 east of Selinsgrove and US 522 to the west.
Anthracite Trail Monticello, NY to Wilkes-Barre via Honesdale and Scranton; now mainly PA 652, US 6, and US 11.
24 Washington-Harrisburg Route Via Frederick and Gettysburg; now mainly US 15.
41 Highway from Reading to Harrisburg Via Lancaster, now mainly US 222 and PA 230 from east to west.


More auto trails were numbered by 1928, including:


14 York Trail York to Baltimore via Red Lion and Stewartstown; now mainly PA 24
17 Benjamin Franklin Highway New Castle to Ebensburg via Kittanning, and Harrisburg to Philadelphia via Reading; now mainly US 422
18 Erie-Lincoln Highway Erie to Beaver Falls via Greenville and New Castle; now mainly PA 18
22 Keystone Trail Wilkes-Barre to Philadelphia via White Haven and Allentown; now mainly PA 309
33 Lykens Valley Trail Millersburg to Stroudsburg via Pottsville and Lehighton; now mainly US 209
44 Buchanan Highway Mount Union to Emmitsburg via McConnellsburg; now mainly US 522 and PA 16
46 Bradford Farmers' Valley Highway Bradford to Smethport; now PA 46
55 Bucktail Trail Lock Haven to Ridgway via Renovo and Saint Marys; now mainly PA 120
64 Horseshoe Trail
Altoona-Bellefonte-Cumberland Trail
Now mainly US 220 south of Williamsport.
66 Anchor Line Fentonville, NY to Smithfield via Warren, Kittanning, and Uniontown; now mainly US 62, PA 66, and US 119
88 Perry Highway Erie to Pittsburgh via Meadville and Mercer; now mainly US 19


By 1927, the numbering system was expanded to include more two-digit numbers beyond the ones listed above. Two-digit numbers were typically assigned to branches off the single-digit routes so that the ones digits of the branches matched the single-digit numbers. For example, 58 and 98 were branches off 8. Other two-digit numbers are not branches but were located near the associated one-digit route. Many two-digit numbers were used more than once at this time, perhaps with the plan of eventually connecting some of them together. Three-digit numbers were not assigned.

A scan of a 1927 road map is available on Harold Cramer's Maps of PA site. Auto trails from across the country are listed on Dave Schul's North American Auto Trails web site.

[More information to come on the 1925 system.]


The 1926 US Highway System (Public Use)

In 1926-27, the US highway system was implemented. This system assigned a new set of numbers that did not change when roads crossed state boundaries, setting up the nation's first interstate highway system. (Here "interstate" indicates a system extending across the country and does not refer to the system of Interstate superhighways built decades later). The major state routes, and some minor state routes, were assigned the new US numbers, but not entirely to Pennsylvania's liking. While some of the major highways that had been first numbered in 1924-26 were given one US highway number (e.g., Roosevelt Highway/7 became US 6), others were given several numbers (e.g., 4 became US 111 south of Harrisburg, US 11 from Harrisburg to Northumberland, US 120 from Northumberland to Williamsport, and US 111 north of Williamsport). Pennsylvania would have preferred a single number along its designated major highways, and so left the state route numbers signed while adding the US highway numbers. The Roosevelt highway, for example, became US 6/PA 7 (dually signed), while the Susquehanna Trail became US 111/PA 4, US 11/PA 4, US 120/PA 4, and US 111/PA 4 (in addition to any numbers from overlapping major highways, such as the William Penn Highway, US 22/3) so that PA 4 could be followed along the entire Susquehanna Trail.


The Modern 1928 System (Public Use)

In 1928, the "modern" state route numbering system was implemented. After several of the US highway system's initial flaws were corrected in its first two years (an interesting combination of renumberings and relocations, including US 19, US 22, US 120, US 422, and more) and that system seemed more finalized, Pennsylvania decided to revamp its state route numbering system. The US system used a parent-child system, where main "parent" routes were given one- and two-digit numbers, and branch or "child" routes of those routes were given three-digit numbers whose last two digits matched the parent. (Note that this system paralleled the 1925 state route system, also a parent-child system, where two-digit routes were branches off the one-digit routes, and the last digit matched.) The new state route system established one- and two-digit parent routes in a style similar but opposite to those of the US highway system. Two-digit odd numbers were assigned to east-west routes, and even numbers assigned to north-south routes, the reverse of the US highway system. The new state route system also established both child (101-799) and spur routes (800-999), which were given three-digit numbers based on the connecting parent route. When this 1928 system was implemented, many of the earlier numbers were changed.

Several of the named trans-state highways kept their numbers from 1925: 1 (duplicated US 1), 2, 3, 4, 5, 7, 8, 9, 12, 17, and 41. Others were renumbered to avoid duplication with US highway numbers (6 became 10 and 60, 11 became 81, 13 became 17 and 33, and 19 became 39). PA 1 may have remained because its child routes (101-701) would not duplicate any US highway numbers, and nearly all of PA 1 also had a US highway number that eventually replaced it (US 30 and US 1). Additionally, the sixteenth trans-state highway, 24, became part of 14, and 24 was reassigned to the east.


The Interstate Highway System (Public Use)

The Eisenhower Interstate Highway System was developed in the 1950s and mostly completed by 1980. This system of high-speed freeways (limited-access highways) replaced almost all at-grade intersections with interchanges and allowed nearly uninterrupted travel across the country. This system supplemented the long-established state and US highway systems.


The 1980s State Route System (Internal Use)

The State Route (SR) system replaced the internal LR system of 1911, which suffered from the peculiarity that many routes had vastly different internal (LR) and external (PA, US, I) numbers, and often a signed, externally numbered route would change LR numbers several times. The SR system assigned one-, two-, and three-digit numbers to the signed routes so that the internal and external routes matched in almost every case. For example, PA 235 became SR 235, or since all the SRs are often written consistently as four-digit numbers with padded zeroes, PA 235's SR may also be written as SR 0235. These SR numbers extend along the entire length of almost all signed state, US, and Interstate routes. Additionally, all other state-maintained roads, such as secondary roads, interchange ramps, truck escape ramps, and rest areas, were given four-digit numbers above 1000. The SR numbers above 1000 are specific to each county, and one can find SR 1001, SR 1002, and other low-numbered such SR routes in all 67 counties, including Philadelphia. SR numbers and their segment numbers can be found on little white signs along SR routes.



This rest of this web site will give a general overview to the numbering systems used in Pennsylvania since 1928, with plenty of examples. This site also provides a detailed look at how each of the approximately 900 routes (past and present) fit (or do not fit) into the numbering systems.

If you wish to follow along with a couple of road maps, I would suggest downloading the latest PENNDOT map and browsing the 1929 map available online at Bruce Harper's site in three pieces (west, middle, and east).


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