The numbering plan for US Highways, Road links, and Web site credits

Numbering convention for United States Numbered Highways
The U.S. Numbered Highway System is not a true Federal program for roadways, but a series of interconnected state highways with a unified numbering plan for the purpose of aiding navigation. They were chosen initially from higher traffic roads that had previously identified by the states as deserving of Federal Aid. Not every Federal Aid route was given a US number. US highways are built and maintained by the individual states and funded in the same manner as any other state highway. In most states, they are simply a state highway with a different shield. Numbering and signing of US routes is approved by the American Association of State Highway and Transportation Officers (AASHTO). Participation the the US Route System is voluntary. States are not bound by Federal Law to comply with US route designations.
New US highways approved by AASHTO must meet with current design standards. The original routes were laid out with trip continuity in mind, but no firm design standards. In fact, paving of the US route system was not completed until the 1960's.

• US routes are all in the contiguous 48 states and have 1, 2, or 3 digit numbers
  • Even numbers run east to west; increasing to the south
    • Principal routes are one or two digits (abbreviated as 2dus) and end in 0: US 10 to US 90
    • Existing range is US 2 to US 98
    • US 0 was specifically avoided in the initial plan. An extended US 2 occupies what would normally have been its route.
    • US 100 would have been considered a two-digit route, if assigned.
  • Odd numbers run north to south; increasing to the west
    • Principal routes are one or two digits (with a single three digit exception) and end in 1: US 1 to US 101
    • Existing range is US 1 to US 101
    • US 101 is considered to be a two-digit route for the purposes of the numbering plan.
    • It is clear from the initial routings chosen in 1925 and 1927 that route numbers ending in "5" were not planned to be principal routes, unlike Interstate numbering.
  • Increments of low-order digits fill in the grid
    • e.g. US 20, US 22, US 24, ... US 30 - Even Numbered
    • e.g. US 21, US 23, US 25, ... US 31 - Odd Numbered
    • In the beginning. some routes ended up out of place due to compromises. US 6 was placed below US 20, presumably so Boston could have a major x0 route. US 9, US 13, and US 17 run east of US 1 in whole or in part, probably due to the desire of the states to have the main route though their capitals. US 16 was placed above US 12 in Michigan and Wisconsin. (US 48) [I] was placed below US 50 in California. US 11, US 52, and (US 66) are diagonal much of their lengths as opposed to filling a grid.
    • In the 1930's more routes were added apparently outside the grid. US 44 and US 46 were added north of US 30. US 59 is not east of US 61 on most of its route. US 96 [II] was assigned over US 59's former route in east Texas, making it a north-south route, while US 59 was routed southwestly over (US 96) [I]. US 98 ended up assigned north of US 92 and (US 94) along Florida's northeastern Gulf coast.
    • Later routes have been placed oddly as well : US 56 was assigned north of the existing US 54 in 1957. US 57 was added out of the normal numbering grid in the US numbering system by Texas in 1971 as an extension of Mexican Federal Highway 57, this also replaced a short lived Texas State Highway 57.
  • In addition, an increment of 3rd high order digits (3dus) denote branch highways or spur routes.
    • e.g. US 166, US 266, (US 366), (US 466), (US 566),(US 666)
    • Initially, these were numbered sequentially, from north to south and/or from east to west along the route they branched from. Routes added later were numbered in order of creation, like (US 541) [1932-1951] and US 641 [1955-now] or re-used older numbers, like the current US 180 [Old 1926-1935, New 1944-now].
    • Originally at least one end of a 3dus was to connect to its parent 2dus or a related 3dus. US 163 [II] in UT & AZ, assigned 1971, is among the exceptions which never connected. US 310 no longer connects to its parent route because of the truncation of US 10 in 1986. US 138's parent highway, US 38, was decommissioned in favor of US 6 in 1932. US 220 connected to US 120 when first assigned in 1926, but not to US 20. US 164 [II] was assigned in the late 1960's to Colorado, New Mexico, and Arizona, without ever connecting to US 64.
    • US 400 is the only 3dus ever to be assigned without a obvious parent route, it could be the third branch of a hypothetical US 0 or US 100.
  • US Divided-number Routes are of the form nd where d is {N|S|E|W}
    • e.g. US 70N, US 70S and (US 99E), (US 99W).
    • These were meant to be equal 50-50 splits in the highway, and were added as a compromise to get the numbering plan accepted. AASHTO has never liked the concept, and has been trying to eliminate the splits practically since they were first approved. More information on these routes is on the Divided (split) routes page.

• In 1970, AASHTO revised its guidelines for US highways. See R.C. Moeur's site for the full text.
  AASHTO policies do not carry the weight of law and are not hard-and-fast rules.
  • No new divided route numbers; existing ones should be eliminated.
    • US 25 still splits into US 25E and US 25W, and many other routes have E / W splits.
  • No new numbers for routes wholly in a single state.
    • US 57, approved for 1971, is a Texas only route.
  • Existing single state routes less than 300 miles long should be eliminated.
    • US 266 in Oklahoma and US 311 in North Carolina are very short routes.

• New numbers approved by AASHTO in recent years include what some people see as a "Future Interstate Corridor 400 series" based on multiples of 12.5
  I would be floored if AASHTO permits a US 437, the next number in this progression.
  • US 400 (1994), the third branch of a fictional US 0 or 100, is (or was) on the preferred future route of I-66.
  • US 412 (1982), which does not connect to US 12 or any branch of it, is a congressional high priority corridor (possible future interstate).
  • US 425 (1989), which does not connect to US 25, is the fourth branch of US 25 after the hypothetical routes US 125, US 225, and US 325, and is highly unlikely to be an Interstate corridor, ever. Well, maybe they will extend I-540, thus justifying this odd designation. This numbering was either silly, stupid, or careless. US 265 would have worked just as well.

The routes initially planned in 1925 . . . . . The routes agreed upon Nov-11-1926

Additionally, auxilliary signs further define the US highways, these are listed at Alternate US highways: Bannered routes.
Sometimes these banners are signed as suffixes, like US 89A = Alternate US 89 in Arizona.
Cardinal directions, such as WEST are placed above the shield.
Other banners indicate additions to the US highway system
ALTERNATE ALT OPTIONAL OPT : a longer or less well constructed loop along the main route, but would have been suitable as the mainline if a better route was not available. Optional is a old name for this type.
BUSINESS BUS CITY : a loop leading through the heart of a city's commercial area, generally the original route though town. City is the older name for the type.
BYPASS BYP RELIEF BELT LINE : a loop leading around the heart of a city's commercial / most congested area, generally recently built.
DETOUR : an interim route used while the main route is under construction. Usually used for mainline traffic. Uses an Orange banner.
HISTORIC OLD FORMER : previous alignments, not acknowledged by AASHTO as banner types.
SCENIC : a little used subset of Alternate.
SPUR CONNECTOR CONN : a branch route connecting to a specific location along the road. Connector Routes, a subset of the type, have been appearing recently in SC and other states.
TEMPORARY TEMP: an interim route used while the main route is under initial construction, or when the proposed route is not yet finalized. Used for mainline traffic.
TOLL : an alternate-type route loop you have to pay to drive on. Rarely used with US routes.
TRUCK : a subset of Bypass meant for trucks and other big vehicles.

These are a few of my favorite Road Links

The official offramp from this site - links mostly focused on roads, history, and art

Throughout this website I linked to various state-specific websites. This page has the complete list of them with authors

Looking for even older roads? Before U.S. Highways? Dave Schul lists a multitude of the named Auto Trails that criss-crossed North America and still grace many city streets, highways and backroads today. Click here for information on the Lincoln Highway, the Dixie Highway and many others.

Are all these lists and tables boring you? Do you want to see photographs of the ends of US routes? Dale Sanderson maintains a collection of these on his website.

Kurumi's site has information on Connceticut, three digit interstates and there are nifty Java programs to play with like the ever-popular Signmaker.

The International House of ZZYZX has loads of information on the two digit interstates

Run by Alex Nitzman and Andrew Field, this omnibus site covers Business Interstates, Lost Highways, Road Pictures, Future Interstate Corridors, and has one of the more complete collection of road site links.

James Lin's highway site. His extensive link list emphasizes road-fan sites. He maintains a picture or graphic of just about every type of route maker. This is also a major source of information on the Lincoln Highway.

The data from the former "Information Superhighways" links site maintained by J.P. Kirby has been incorporated to the DMOZ online directory project under the Recreation: Roads and Highways Category, includes many official and road-fan sites.

This is the host of the misc.transport.road "Frequently Asked Questions". This site may have the answer to every question you ever had about highways, and a few you did not know you had. It also hosts the popular online links to Driver's manuals.

FHWA's Office of Infrastructure hosts this series of in depth articles by W. Lee Mertz and Richard F. Weingroff on the birth and growth of the United States highway systems from the Federal point of view. It is a facinating read, well worth your time.

Kim Russell's US Highways Website - A concise and easy to understand overview of each US numbered highway in existence and a few he'd like to see added.

Michelle Skinner's Interstate Website - A concise and easy to understand overview of each Interstate in existence and a few she'd like to see added.

If you can't find what you are looking for at or from one of these sites, it probably does not exist yet.

Source material:
Report of Joint Board on Interstate Highways, Appendix VI, Oct. 30, 1925; American Highways, Vol VI. No. 2, April 1927; United States Numbered Highways 1989 ed. - AASHTO (with Revisions); Rand McNally and Gallup Road Atlases were used to confirm information, supplemented by other road atlases and maps including those made by AAA. I also utilized oil company and official state maps, too numerous to mention here. Visit your local public library, you will be astounded at the maps they keep.
Helpful information was also found in an article in AASHTO Quarterly, Spring 1997, From Names to Numbers: The Origins of the U.S. Numbered Highway System by Richard Weingroff, FHWA.

Acknowlegements:
My grandfather, Perley Vaughn Droz (1915-1999), died September 22nd in Ft. Myers, Florida following an extended illness. More information about him and my family is here.

Dr. James P. G. Sterbenz's web site and text file were important sources of initial data and the primary inspiration for this site. I learned how to code HTML by studying it. I believe it to be the original road fan website dedicated to US highways. Much thanks to him and Jim Lindsay, for his site on the 1961 US highway system.

Thanks also go out to following people and contless others for their assistance, information, and comments: James Allen, Steve Anderson, David Backlin, Thomas Baird, Mike Ballard, Edward Barfield, Chris Bessert, Ian Beverly, Russell Blau, Mark Bozanich, Tim "Bandit" Brown, Rich Carlson, Hollis Carroll, Bob Chessick, Casey Cooper, Mark J. Cuccia, Jeremy Dailey, H.B. Elkins, Jon Enslin, Marc Fannin, Andrew Field, Adam Froehlig, Chris Geelhart, Joe Gillis, Brandon Gorte, Alan Hamilton, Jason Hancock, Landry Heaton, Austin Hellwig, Richard Helms, Paul Henry, Stephen Hill, John Hobson, Pete Jenior, Kevin Johnson, Chris Kelly, Mike Kendricks, Richie Kennedy, J.P. Kirby, Jeff Kitsko, Dr. Joe Knetch, Chris Knight, Jeremy Lance, John Lansford P.E., Jeff Leadbetter, Zachary Maillard, Chris Martin, Chris Marysz, Merle McClelland, Dan Mengel, Dan "Spui" Moraseski, Mike Moroney, Alex Nitzman, Cheryl Nowka, Scott "Kurumi" Ogelsby, Brian Powell, Mike Pruett II, William Riddle IV, Steve Riner, Mark Roberts, Matt Roberts, James Rumbarger, Jim Russell, Chris "Calvin" Sampang, Matthew Salek, Paul Schlichtman, Dave Schul, James Schul, John Simpson, Richard Simpson III, C.C. Slater, Larry Smith, David Stanek, Mark Stauter, Matt "J. Vincent" Steffora, Dan Stober, David Strong, David Sturm, Steven Taylor, James Watts, Richard Weingroff, Mike Wiley, Steve Williams, J.P. Wing, and William Yurasko. I also would like to thank the folks who post on misc.transport.road, my favorite usenet newsgroup, dedicated to highway travel. If you belong on this list, please remind me. I don't want to forget anyone.
Some Animated Graphics from: http://www.clipartconnection.com/ and http://www.animfactory.com/, others I made myself with WWW Gif animator.

A definition of the abbreivations used on this site as well as some of the more obscure termini can be found here.

E-mail me with comments, suggestions, additions, broken links, and omissions

Last update to this page on Monday, May 23, 2005. Any original work or research on this page (c) R . Droz