In October of 1999, a discussion began in m.t.r
about the basis of highway numbering in the Commonwealth of Pennsylvania.
On October 26, 1999 Gene Yao had this post to m.t.r.
A year later in October 2000, Steve Walter added more insight to the state
route history.
Phase 1: 1911-1924
The original system as adopted by PDH (after the Sproul Road Bill).
Numbering was somewhat clustered and was consecutive. Routes were assigned
to relatively uniform lengths of road, ranging from 25 to 75 miles or so.
I would have to look at maps and photocopies of maps I have at home, but
in 1911, the highest route was in the 290's; in 1924, the highest route
number was well into the 300's. Any numbers that have carried through to
today are purely coincidental, although I do know of one offhand; ironically,
this was part of what is now PA 66.
Phase 2: 1925-1927
This grid system, which was an early adaptation of its parent-child
successor, incorporated 1 and 2 digit highway numbers (no 3DPAs yet), resulting
in many disjointed sections for particular route numbers. This phase however
did introduce many highway numbers which are still in place today, such
as 8, 63, and 73. As of 1927, all numbers 1 through 28 inclusive had been
assigned, all x1 through x8 from the 30's to the 90's, and 99.
Phase 3: 1928-1941
The parent-child (or trunk and branch) system that we are all familiar
with was initially implemented, concomitant with the adoption of U.S. Highway
routes. At this point, 3DPAs were introduced, including the 8xx and 9xx
routes. Pursuant to the parent-child system, note that many U.S. Highways
also seem to have hidden PA numbers. For example, US 6's "hidden" PA route
was 7, which makes sense since it had been PA 7 prior to the US System
adoption. However, US 40 (which had been PA 11) has a "hidden" number of
PA 81. The reason for this would probably point to the existence of US
11.
Phase 4: 1942-1960
A continuation of Phase 3, except many 3DPAs lost their status during
the war. Also, it was about this time that new route numbers were randomly
assigned instead of systematically
Phase 5: 1961-present
As a reaction to the Interstate System, Pennsylvania decided to renumber
PA Highways which used Interstate numbers planned for the Keystone State.
For example, PA 70 became PA 171, and PA 84 became PA 287. Significant
renumbering not related to Interstates also occurred in the early years
of this period. Examples of this included then PA 12 (partially replaced
by 191, partially decommissioned), PA 37 (replaced by PA 434), and the
eastern part of PA 45 (replaced by PA 248). Many US Highways (111, 120,
122, 140, 230, 309, 611) were also reassigned as PA routes at this time.
Ironically, any subsequent additions to the Interstate Highway System (e.g.
380, 99, 86) have not resulted in a renumbering of like numbered state
routes.
One could argue that this last phase could be further into two phases, with the former encompassing 1961-1972 and the latter 1973 to present. Each reflects the relative turbulence with regard to route number reassignment; the former time period saw many more changes than the latter. Also, the Interstate/PA route duplication issue dovetails quite nicely with this break as well.
The Logic: by Gene Yao
Its often been said that PA's state highways have no logic. However, if you trace the decommissioned routes and disregard the newest routes (which violate the rules), a logical system can be seen. With a few exceptions, 2d state highways are clustered based on their second digit. The 2d highways ending in even numbers generally go north-south and are clustered from the x2's in the east to the x8's in the west. The 2d highways ending in odd numbers generally go east-west and are clustered from the x1's in the south to the x9's in the north. Breaking it down:
Odds:
x1's - 21, 31, 41, and 61 are all in the southern part of the state. As for the missing numbers: PA 1 is now US 30, PA 11 is now US 40, and PA 71 is now I-70. All three are in southern PA. PA 81 was never assigned. The exceptions are PA 61 and former PA 91.
x3's - 3, 23, 33, 63, and 73 are all in the southern part of the state (generally above the 1's). The decommissioned routes are PA 13 (ran from Harrisburg to Philly), original PA 43 (the Schuylkill Expressway), and PA 83 (ran in SE PA). PA 53 and 93 are the only exceptions.
x5's - 25, 35, 45, 65, and 85 are all in the middle swathe of the state. PA 95 is now PA 192, also in the central swathe. PA 15 and 55 were never assigned. The one glaring exception is PA 5 (perhaps a newer designation?). PA 75 is also an exception
x7's - 27, 77, 87, and the northern 97 are basically in the northern part of the state. The decommissioned routes are: PA 7 (now US 6) and PA 57 (now PA 157: Oil City to Fryburg). PA 37, 47, and 67 were never assigned (owing to the sparse population of the northern tier of the state). PA 17 is an exception. Southern PA 97 is also an exception but that is mainly because that designation is relatively new (having been given to a now decommissioned US route).
x9's - northern 29, 49, 59, 69, 89, and 99 are all in the northern part of the state. The decommissioned routes are: original PA 9 (now US 20) and PA 79 (now PA 178 in NE PA). All three ran in the northern part of the state. PA 39 and former PA 19 are the exceptions.
Evens:
x2's - 32, 42, 52, 72, 82, and 92 are all in eastern PA. So were the decommissioned routes: PA 2 (now PA 611 and US 11), PA 12 (now US 1), and PA 62 (now PA 100). PA 22 was never assigned.
x4's - 14, 24, 34, 44, 54, 64, 74, and 94 are all in the east central part of the state. So were the decommissioned routes: PA 4 (ran along the Susquehanna River) and PA 84 (now PA 287).
x6's - 16, 26, 36, 46, 56, 66, 86 and 96 are generally in the west central part of the state. So were the decommissioned routes: PA 6 (now US 119 and US 219) and PA 76 (now PA 655).
x8's - 8, 18, 28, 38, 48, 58, 68, and 98 are all in western PA. So was PA 78 (now PA 173).
x0's - It seems that PA originally did not issue x0's. This explains why there's no logic in the placement of x0's. Most x0's replaced older designations: PA 10 (replaced US 122), PA 50 (replaced part of PA 28), and PA 60 (part new road and part replacement of old route of US 22/30). PA 20, 30, and 40 were never assigned. Former routes PA 70, PA 80 and PA 90 were exceptions and I suspect these were also later additions.
This explains the 1dpa's (which are the primary cross state routes See Jeff Kitsko's PA State Highways Page for further information.) and the 2dpa's (which are branches off the 1dpa's.
3dpa's are basically branches off their parent routes for example PA 148 is a branch off of PA 48. This rule generally applies to 100-700 series routes. The 800-900 series are basically clustered in random order in various regions of the Commonwealth.
This numbering system basically was the status quo until the creation of the US Highway System in 1927. At that time, many of the primary state routes became US Highways again see Jeff Kitsko's PA State Highways Page for further information. PA also did not want to duplicate a state route with a US route.
The next major change in the PA Numbering System came with the advent
of the Interstate Highway System. Again, PA did not want to have duplicate
numbers. For example PA 80 became current day PA 380.
Of course there are exceptions this is Pennsylvania right!!!!. Most exceptions occur in the duplication of a PA route with a US or Interstate Route. The exceptions are as follows:
Pennsylvania has resurrected some old numbers. They include:
Page Created: March 25, 2000
Last Updated: March 31, 2006
© 2000-06 William Lawson