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United States Numbered Highways

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United States Numbered Highway System
US shield evolution.svg
Map of the present U.S. Highway network
System information
Maintained by state or local governments; numbers and routings assigned by AASHTO[lower-alpha 1]
Length: 157,724 mi[lower-alpha 2] (253,832 km)
Formed: November 11, 1926[1]
Highway names
US Routes: U.S. Highway nn (US nn)
U.S. Route nn (US nn)
System links
  • United States Numbered Highways

The system of United States Numbered Highways (often called U.S. Routes or U.S. Highways) is an integrated network of roads and highways numbered within a nationwide grid in the contiguous United States. As the designation and numbering of these highways were coordinated among the states, they are sometimes called Federal Highways, but the roadways have always been maintained by state or local governments since their initial designation in 1926.

The route numbers and locations are coordinated by the American Association of State Highway and Transportation Officials (AASHTO).[4] The only federal involvement in AASHTO is a nonvoting seat for the United States Department of Transportation. Generally, north-to-south highways are odd-numbered, with lowest numbers in the east, the area of the founding thirteen states of the United States, and highest in the west. Similarly, east-to-west highways are typically even-numbered, with the lowest numbers in the north, where roads were first improved most intensively, and highest in the south. Major north–south routes have numbers ending in "1" while major east–west routes have numbers ending in "0". Three-digit numbered highways are spur routes of parent highways but are not necessarily connected to their parents. Some divided routes exist to provide two alignments for one route, even though many splits have been eliminated. Special routes, usually posted with a banner, can provide various routes, such as an alternate, bypass or business route, for a U.S. Highway.

Before the U.S. Routes were designated, auto trails designated by auto trail associations were the main means of marking roads through the United States. In 1925, the Joint Board on Interstate Highways, recommended by the American Association of State Highway Officials (AASHO), worked to form a national numbering system to rationalize the roads. After several meetings, a final report was approved by the U.S. Department of Agriculture in November 1925. They received complaints from across the country about the assignment of routes, so the Board made several modifications; the U.S. Highway System was approved in November 1926. As a result of compromises made to get the U.S. Highway System approved, many routes were divided, with alignments to serve different towns. In subsequent years, AASHTO called for such splits in U.S. Routes to be eliminated.

Expansion of the system continued until 1956, when the Interstate Highway System was formed. After construction was completed, many U.S. Routes were replaced by Interstate Highways for through traffic. Despite the Interstate system, U.S. Highways still form many important regional connections, and new routes are still being added.

System details

US 50.svg  US 50 (1961 cutout).svg
The U.S. Route shield is printed on a square blank with a black background. California is the only state to use an older cut-out design.

In general, U.S. Routes do not have a minimum design standard, unlike the later Interstate Highways, and are not usually built to freeway standards. Some stretches of U.S. Routes do meet those standards. Many are designated using the main streets of the cities and towns through which they run. New additions to the system, however, must "substantially meet the current AASHTO design standards".[4] As of 1989, the United States Numbered Highways system has a total length of 157,724 miles (253,832 km).[3]

Except for toll bridges and tunnels, very few U.S. Routes are toll roads. AASHTO policy says that a toll road may only be included as a special route, and that "a toll-free routing between the same termini shall continue to be retained and marked as a part of the U.S. Numbered System."[4] U.S. Route 3 (US 3) meets this obligation; in New Hampshire, it does not follow tolled portions of the Everett Turnpike. But US Routes in the system do use parts of four toll roads:[5]


The two-digit U.S. Routes follow a simple grid in the contiguous United States, in which odd-numbered routes run generally north to south and even-numbered routes run generally east to west. (US 101 is considered a two-digit route, its "first digit" being 10.) The numbering pattern for U.S. Routes was established first: U.S. Routes proceed from low even numbers in the north to high even numbers in the south, and from low odd numbers in the east to high odd numbers in the west. Numbers ending in 0 or 1 (and US 2[6]), and to a lesser extent in 5, were considered main routes in the early numbering, but extensions and truncations have made this distinction largely meaningless. For example, US 6 was until 1964 the longest route (that distinction now belongs to US 20).[7]

In the 1950s, the numbering grid for the new Interstate Highway System was established as intentionally opposite from the US grid. Its numbers increase from west-to-east and south-to-north, to keep identically numbered routes geographically apart in order to keep them from being confused with one another.[7]

In the US Highway system, three-digit numbers are assigned to spurs of one or two-digit routes. US 201, for example, splits from US 1 at Brunswick, Maine, and runs north to Canada.[8] Not all spurs travel in the same direction as their "parents"; some are connected to their parents only by other spurs, or not at all, instead only traveling near their parents. As originally assigned, the first digit of the spurs increased from north to south and east to west along the parent; for example, US 60 had spurs, running from east to west, designated as US 160 in Missouri, US 260 in Oklahoma, US 360 in Texas, and US 460 and US 560 in New Mexico.[9] As with the two-digit routes, three-digit routes have been added, removed, extended and shortened; the "parent-child" relationship is not always present. For example, several spurs of the decommissioned US 66 still exist. US 191 travels from border to border although its parent, US 91, has been largely replaced by Interstate 15 (I-15).[8][10]

In addition, US 163, designated in 1970, is nowhere near US 63.[8][11] The short US 57, approved c. 1970, connects to Federal Highway 57 in Mexico, and lies west of former US 81.[8]

Several routes approved since 1980 do not follow the numbering pattern:

While AASHTO guidelines specifically prohibit Interstate Highways and U.S. Routes from sharing a number within the same state[12] (which is why there are no Interstates 50 or 60), the initial Interstate numbering approved in 1958 violated this with I-24 and US 24 in Illinois and I-40, I-80, US 40 and US 80 in California (US 40 and US 80 were removed from California in its 1964 renumbering).[10]

Some recent and proposed Interstates, some of them out of place in the grid, also violate this: I-41 and US 41 in Wisconsin (which will run concurrently),[13] I-49 and US 49 in Arkansas,[8][14] I-69 and US 69 in Texas,[8][15] and I-74 and US 74 in North Carolina (which run concurrently).[16]

Some two-digit numbers have never been applied to any U.S. Route, including 39, 47, 86 and 88.

Divided and special routes

Since 1926, some divided routes were designated to serve related areas, and designate roughly-equivalent splits of routes. For instance, US 11 splits into US 11E (east) and US 11W (west) in Bristol, Virginia, and the routes rejoin in Knoxville, Tennessee. Occasionally only one of the two routes is suffixed; US 6N in Pennsylvania does not rejoin US 6 at its west end. AASHTO has been trying to eliminate these since 1934;[17] its current policy is to deny approval of new split routes and to eliminate existing ones "as rapidly as the State Highway Department and the Standing Committee on Highways can reach agreement with reference thereto".[4]

Special routes—those with a banner such as alternate or bypass—are also managed by AASHTO.[4] These are sometimes designated with lettered suffixes, like A for alternate or B for business.[18]


The official route log, last published by AASHTO in 1989, has been named United States Numbered Highways since its initial publication in 1926. Within the route log, "U.S. Route" is used in the table of contents, while "United States Highway" appears as the heading for each route. All reports of the Special Committee on Route Numbering since 1989 use "U.S. Route", and federal laws relating to highways use "United States Route" or "U.S. Route" more often than the "Highway" variants.[19] The use of U.S. Route or U.S. Highway on a local level depends on the state, with some states such as Delaware using "route" and others such as Colorado using "highway".[20][21]


Early auto trails

In 1903, Horatio Nelson Jackson became the first documented person to drive an automobile from San Francisco to New York using only a connection of dirt roads, cow paths, and railroad beds. His journey, covered by the press, became a national sensation and called for a system of long distance roads.[22]

In the early 1910s, auto trail organizations—most prominently the Lincoln Highway—began to spring up, marking and promoting routes for the new recreation of long-distance automobile travel. While many of these organizations worked with towns and states along the route to improve the roadways, others simply chose a route based on towns that were willing to pay dues, put up signs, and did little else.[1]


Wisconsin was the first state in the U.S. to number its highways, erecting signs in May 1918.[1] Other states soon followed. In 1922 the New England states got together to establish the six-state New England Interstate Routes.[23]

Behind the scenes, the federal aid program had begun with the passage of the Federal Aid Road Act of 1916, providing 50% monetary support from the federal government for improvement of major roads. The Federal Aid Highway Act of 1921 limited the routes to 7% of each state's roads, while 3 in every 7 roads had to be "interstate in character". Identification of these main roads was completed in 1923.[1]

The American Association of State Highway Officials (AASHO), formed in 1914 to help establish roadway standards, began to plan a system of marked and numbered "interstate highways" at its 1924 meeting. AASHO recommended that the Secretary of Agriculture work with the states to designate these routes.[1]

Secretary Howard M. Gore appointed the Joint Board on Interstate Highways, as recommended by AASHO, on March 2, 1925. The Board was composed of 21 state highway officials and three federal Bureau of Public Roads officials. At the first meeting, on April 20 and 21, the group chose the name "U.S. Highway" as the designation for the routes. They decided that the system would not be limited to the federal-aid network; if the best route did not receive federal funds, it would still be included. The tentative design for the U.S. Highway shield was also chosen, based on the shield found on the Great Seal of the United States.[1]

The auto trail associations rejected the elimination of the highway names. Six regional meetings were held to hammer out the details—May 15 for the West, May 27 for the Mississippi Valley, June 3 for the Great Lakes, June 8 for the South, June 15 for the North Atlantic, and June 15 for New England. Representatives of the auto trail associations were not able to formally address the meetings. However, as a compromise, they talked with the Joint Board members. The associations finally settled on a general agreement with the numbering plans, as named trails would still be included. The tentative system added up to 81,000 miles (130,000 km), 2.8% of the public road mileage at the time.[1]

US 32 Iowa 1926 shield marker
US 28 Oregon 1948 shield marker
1926 and 1948 versions of the U.S. Route shield

The second full meeting was held August 3 and 4, 1925. At that meeting, discussion was held over the appropriate density of routes. William F. Williams of Massachusetts and Frederick S. Greene of New York favored a system of only major transcontinental highways, while many states recommended a large number of roads of only regional importance. Greene in particular intended New York's system to have four major through routes as an example to the other states. Many states agreed in general with the scope of the system, but believed the Midwest to have added too many routes to the system. The group adopted the shield, with few modifications from the original sketch, at that meeting, as well as the decision to number rather than name the routes. A preliminary numbering system, with eight major east–west and ten major north–south routes, was deferred to a numbering committee "without instructions".[1]

After working with states to get their approval, the committee expanded the highway system to 75,800 miles (122,000 km), or 2.6% of total mileage, over 50% more than the plan approved August 4. The skeleton of the numbering plan was suggested on August 27 by Edwin Warley James of the BPR, who matched parity to direction, and laid out a rough grid. Major routes from the earlier map were assigned numbers ending in 0, 1 or 5 (5 was soon relegated to less-major status), and short connections received three-digit numbers based on the main highway from which they spurred. The five-man committee met September 25, and submitted the final report to the Joint Board secretary on October 26.[1] The board sent the report to the Secretary of Agriculture of October 30, and he approved it November 18, 1925.[9]

Disagreement and refinement 1925–26

The "final" U.S. Highway plan as approved November 11, 1926

The new system was both praised and criticized by local newspapers, often depending on whether that city was connected to a major route. While the Lincoln Highway Association understood and supported the plan, partly because they were assured of getting the US 30 designation as much as possible, most other trail associations lamented their obsolescence. At their January 14–15, 1926 meeting, AASHO was flooded with complaints.[1]

In the Northeast, New York held out for fewer routes designated as US highways. The Pennsylvania representative, who had not attended the local meetings, convinced AASHO to add a dense network of routes, which had the effect of giving six routes termini along the state line. (Only US 220 still ends near the state line, and now it ends at an intersection with future I-86.) Because US 20 seemed indirect, passing through Yellowstone National Park, Idaho and Oregon requested that US 30 be swapped with US 20 to the Pacific coast.[1]

Many local disputes arose related to the committee's choices between designation of two roughly equal parallel routes, which were often competing auto trails. At their January meeting, AASHO approved the first two of many split routes (specifically US 40 between Manhattan, Kansas and Limon, Colorado and US 50 between Baldwin City, Kansas and Garden City, Kansas). In effect, each of the two routes received the same number, with a directional suffix indicating its relation to the other. These splits were initially shown in the log as—for instance—US 40 North and US 40 South, but were always posted as simply US 40N and US 40S.[1]

The most heated argument, however, was the issue of US 60. The Joint Board had assigned that number to the Chicago-Los Angeles route, which ran more north–south than west–east in Illinois, and then angled sharply to the southwest to Oklahoma City, from where it ran west to Los Angeles. Kentucky strongly objected to this designated route, as it had been left off any of the major east-west routes, instead receiving the US 62 designation. In January 1926, the committee designated this, along with the part of US 52 east of Ashland, Kentucky, as US 60. They assigned US 62 to the Chicago-Los Angeles route, contingent on the approval of the states along the former US 60. But Missouri and Oklahoma did object—Missouri had already printed maps, and Oklahoma had prepared signs. A compromise was proposed, in which US 60 would split at Springfield, Missouri, into US 60E and US 60N, but both sides objected. The final solution resulted in the assignment of US 66 to the Chicago-Los Angeles portion of the US highway, which did not end in zero, but was still seen as a satisfyingly round number.[1] Route 66 came to have a prominent place in popular culture, being featured in song and films.

With 32 states already marking their routes, the plan was approved by AASHO on November 11, 1926.[1] This plan included a number of directionally split routes, several discontinuous routes (including US 6, US 19 and US 50), and some termini at state lines.[24] By the time the first route log was published in April 1927, major numbering changes had been made in Pennsylvania in order to align the routes to the existing auto trails.[25] In addition, U.S. Route 15 had been extended across Virginia.[26]

Much of the early criticism of the U.S. Highway System focused on the choice of numbers to designate the highways, rather than names. Some thought a numbered highway system to be cold compared to the more colorful names and historic value of the auto trail systems. The New York Times wrote, "The traveler may shed tears as he drives the Lincoln Highway or dream dreams as he speeds over the Jefferson Highway, but how can he get a 'kick' out of 46, 55 or 33 or 21?"[7] (A popular song later promised, "Get your kicks on Route 66!") The writer Ernest McGaffey was quoted as saying, "Logarithms will take the place of legends, and 'hokum' for history."[1]

Expansion and adjustment: 1926–56

This sign, photographed in 1941 on US 99 between Seattle, Washington, and Portland, Oregon, illustrates one rationale for a federal highway system: national defense.

When the U.S. numbered system was started in 1925, a few optional routings were established which were designated with a suffixed letter after the number indicating "north", "south", "east", or "west". While a few roads in the system are still numbered in this manner, AASHO believes that they should be eliminated wherever possible, by the absorption of one of the optional routes into another route.

In 1934, AASHO tried to eliminate many of the split routes by removing them from the log, and designating one of each pair as a three-digit or alternate route, or in one case US 37. AASHO described its renumbering concept in the October 1934 issue of American Highways:[17]

"Wherever an alternate route is not suitable for its own unique two-digit designation, standard procedure assigns the unqualified number to the older or shorter route, while the other route uses the same number marked by a standard strip above its shield carrying the word 'Alternate'."

Most states adhere to this approach. However, some maintain legacy routes that violate the rules in various ways. Examples can be found in California, Mississippi, Nebraska, Oregon, and Tennessee. In 1952, AASHO permanently recognized the splits in US 11,[17] US 19, US 25, US 31, US 45, US 49, US 73, and US 99.[17]

For the most part, the U.S. Routes were the primary means of inter-city vehicle travel; the main exceptions were toll roads such as the Pennsylvania Turnpike and parkway routes such as the Merritt Parkway. Many of the first high-speed roads were U.S. Highways: the Gulf Freeway carried US 75,[27] the Pasadena Freeway carried US 66,[28] and the Pulaski Skyway carried US 1 and US 9.[29]

Interstate era 1956–present

1961 version of the U.S. Route shield

The Federal-Aid Highway Act of 1956 appropriated funding for the Interstate Highway System, to construct a vast network of freeways across the country. By 1957, AASHO had decided to assign a new grid to the new routes, to be numbered in the opposite directions as the U.S. Highway grid. Though the Interstate numbers were to supplement, rather than replace, the U.S. Route numbers, in many cases (especially in the west) the US highways were rerouted along the new Interstates.[10] Major decommissioning of former routes began with California's highway renumbering in 1964. The 1985 removal of US 66 is often seen as the end of an era of US highways.[30]

A few major connections not served by Interstate Highways include US 6 from Hartford, Connecticut, to Providence, Rhode Island; US 101 from Los Angeles to San Francisco; and US 93 from Phoenix, Arizona to Las Vegas, Nevada. Three state capitals in the contiguous U.S. are served only by U.S. Routes: Dover, Delaware; Jefferson City, Missouri; and Pierre, South Dakota.

In 1995 the National Highway System was defined to include both the Interstate Highway System and other roads designated as important to the nation's economy, defense, and mobility.

AASHTO is in the process of eliminating all intrastate U.S. Highways less than 300 miles (480 km) in length "as rapidly as the State Highway Department and the Standing Committee on Highways of the American Association of State Highway and Transportation Officials can reach agreement with reference thereto". New additions to the system must serve more than one state and "substantially meet the current AASHTO design standards".[4] A version of this policy has been in place since 1937.[31]

The 1925 routes

The original major transcontinental routes in 1925, along with the auto trails which they roughly replaced, were as follows:[9]

US 10, US 60, and US 90 only ran about two thirds of the way across the country, while US 11 and US 60 ran significantly diagonally. US 60's violation of two of the conventions would prove to be one of the major sticking points; US 60 eventually was designated as US 66 in 1926, and later it became popular in the culture. US 101 continues east and then south to end at Olympia, Washington.[24] The western terminus of US 2 is now at Everett, Washington.[8]

See also


  1. The American Association of State Highway Officials (AASHO) was renamed the American Association of State Highway and Transportation Officials (AASHTO) on November 11, 1973.[2]
  2. As of 1989.[3]


  1. 1.00 1.01 1.02 1.03 1.04 1.05 1.06 1.07 1.08 1.09 1.10 1.11 1.12 1.13 1.14 Weingroff, Richard F. (April 7, 2011). "From Names to Numbers: The Origins of the US Numbered Highway System". Highway History. Federal Highway Administration. Retrieved June 10, 2011.<templatestyles src="Module:Citation/CS1/styles.css"></templatestyles>
  2. Federal Highway Administration (December 4, 2012). "November 13". Highway History. Federal Highway Administration. Retrieved August 18, 2013.<templatestyles src="Module:Citation/CS1/styles.css"></templatestyles>
  3. 3.0 3.1 AASHTO Special Committee on U.S. Route Numbering (1989). United States Numbered Highways (PDF) (5th ed.). American Association of State Highway and Transportation Officials. p. iv. Retrieved March 16, 2012.<templatestyles src="Module:Citation/CS1/styles.css"></templatestyles>
  4. 4.0 4.1 4.2 4.3 4.4 4.5 American Association of State Highway and Transportation Officials (January 2000). "Establishment and Development of United States Numbered Highways" (PDF). AASHTO Transportation Policy Book. AASHTO. Retrieved January 16, 2014.<templatestyles src="Module:Citation/CS1/styles.css"></templatestyles>
  5. Rand McNally (2013). The Road Atlas: United States, Canada & Mexico (Map) (2013 Walmart ed.). Chicago: Rand McNally. p. 32, § A9; p. 83, §§ D15, D19; p. 92, § J8. ISBN 0-528-00626-6.<templatestyles src="Module:Citation/CS1/styles.css"></templatestyles>
  6. "Ask the Rambler: What Is The Longest Road in the United States?". Federal Highway Administration. April 7, 2011. Retrieved April 11, 2010.<templatestyles src="Module:Citation/CS1/styles.css"></templatestyles>
  7. 7.0 7.1 7.2 McNichol, Dan (2006). The Roads that Built America: The Incredible Story of the US Interstate System. New York: Sterling Publishing. ISBN 1-4027-3468-9.<templatestyles src="Module:Citation/CS1/styles.css"></templatestyles>
  8. 8.0 8.1 8.2 8.3 8.4 8.5 8.6 8.7 8.8 8.9 Rand McNally (2009). The Road Atlas and Travel Guide (Map). Scale not given. Chicago: Rand McNally. ISBN 978-0-528-94209-9.<templatestyles src="Module:Citation/CS1/styles.css"></templatestyles>
  9. 9.0 9.1 9.2 Secretary of Agriculture (November 18, 1925). Report of Joint Board on Interstate Highways, October 30, 1925 (Report). US Department of Agriculture.<templatestyles src="Module:Citation/CS1/styles.css"></templatestyles>
  10. 10.0 10.1 10.2 Esso & General Drafting (1966). United States Featuring the Interstate Highway System (Map). [c. 1:3,870,000]. Convent Station, NJ: General Drafting. OCLC 749860157.<templatestyles src="Module:Citation/CS1/styles.css"></templatestyles>
  11. Arizona Department of Transportation. "Arizona DOT Right-of-Way Resolutions". Arizona Department of Transportation. Retrieved March 30, 2008.<templatestyles src="Module:Citation/CS1/styles.css"></templatestyles>
  12. American Association of State Highway and Transportation Officials (January 2000). "Establishment of a Marking System of the Routes Comprising the National System of Interstate and Defense Highways" (PDF). AASHTO Transportation Policy Book. American Association of State Highway and Transportation Officials. Retrieved December 31, 2013.<templatestyles src="Module:Citation/CS1/styles.css"></templatestyles>
  13. Jones, Ben (December 18, 2006). "'Interstate 41' on near horizon". The Post Crescent. Appleton, Wisconsin.<templatestyles src="Module:Citation/CS1/styles.css"></templatestyles>
  14. "Ross (AR04) Newsletter—Interstate 49". Congressman Mike Ross. June 8, 2001. Archived from the original on June 29, 2011. Retrieved January 8, 2014.<templatestyles src="Module:Citation/CS1/styles.css"></templatestyles>
  15. Texas Department of Transportation. "I-69/TTC (Northeast Texas to Mexico)". TxDOT. Archived from the original on December 14, 2007. Retrieved January 8, 2014.<templatestyles src="Module:Citation/CS1/styles.css"></templatestyles>
  16. Woodard, Johnny (October 8, 2008). "I-74 four-lane to Lumberton opened" (PDF). The Laurinburg Exchange. Retrieved June 7, 2009.<templatestyles src="Module:Citation/CS1/styles.css"></templatestyles>
  17. 17.0 17.1 17.2 17.3 Weingroff, Richard F. (April 7, 2011). "US 11 Rouses Point, New York, to New Orleans, Louisiana". Highway History. Federal Highway Administration. Retrieved June 9, 2011.<templatestyles src="Module:Citation/CS1/styles.css"></templatestyles>
  18. For example, compare the following for an alternate route in Ohio:
    • Ohio Department of Transportation Office of Technical Services, GIS/Mapping Section (2011). Official Transportation Map (Map). 1 in=9 mi. Columbus: Ohio Department of Transportation. §§ B2–F2.<templatestyles src="Module:Citation/CS1/styles.css"></templatestyles>
    • Google (May 5, 2013). "Street View of US 20A/SR 15 near Pioneer, OH" (Map). Google Maps. Google. Retrieved May 5, 2013.<templatestyles src="Module:Citation/CS1/styles.css"></templatestyles>
    • Rand McNally (2013). The Road Atlas: United States, Canada & Mexico (Map) (2013 Walmart ed.). 1 mi=12 mi. Chicago: Rand McNally. p. 78. §§ NE2–NE6. ISBN 0-528-00626-6.<templatestyles src="Module:Citation/CS1/styles.css"></templatestyles>
  19. Google searches on for "United States Route", "U.S. Route", "United States Highway" and "U.S. Highway"
  20. Delaware Department of Transportation (2006). "2006 Traffic Count and Mileage Report" (PDF). Delaware Department of Transportation. Retrieved June 10, 2011.<templatestyles src="Module:Citation/CS1/styles.css"></templatestyles>
  21. Colorado Department of Transportation. "Segment Descriptions for Highway 006". Colorado Department of Transportation. Retrieved June 10, 2011.<templatestyles src="Module:Citation/CS1/styles.css"></templatestyles>
  22. Duncan, Dayton; Burns, Ken (2003). Horatio's Drive: America's First Road Trip (1st ed.). New York: Alfred A. Knopf. ISBN 0-375-41536-X.<templatestyles src="Module:Citation/CS1/styles.css"></templatestyles>
  23. "Motor Sign Uniformity". The New York Times. April 16, 1922.<templatestyles src="Module:Citation/CS1/styles.css"></templatestyles>
  24. 24.0 24.1 Bureau of Public Roads & American Association of State Highway Officials (November 11, 1926). United States System of Highways Adopted for Uniform Marking by the American Association of State Highway Officials (Map). 1:7,000,000. Washington, DC: U.S. Geological Survey. OCLC 32889555. Retrieved November 7, 2013 – via University of North Texas Libraries.<templatestyles src="Module:Citation/CS1/styles.css"></templatestyles>
  25. Weingroff, Richard F. (April 7, 2011). "US 22: The William Penn Highway". Highway History. Federal Highway Administration. Retrieved June 9, 2011.<templatestyles src="Module:Citation/CS1/styles.css"></templatestyles>
  26. "United States Numbered Highways". American Highways. American Association of State Highway Officials. April 1927. ISSN 0002-8746.<templatestyles src="Module:Citation/CS1/styles.css"></templatestyles>
  27. Feldstein, Dan (June 27, 1999). "A rare quiet interlude for area's first freeway/ Next major upgrade: Causeway in 2002". Houston Chronicle. Retrieved June 9, 2009.<templatestyles src="Module:Citation/CS1/styles.css"></templatestyles>
  28. Correspondence between the Division of Highways and American Association of State Highway Officials, transcribed at "State Route 66". California Highways. Retrieved June 10, 2011.<templatestyles src="Module:Citation/CS1/styles.css"></templatestyles>[unreliable source?]
  29. Rand McNally (1946). Road Atlas (Map). Scale not given. Chicago: Rand McNally. p. 42. New York and Vicinity inset.<templatestyles src="Module:Citation/CS1/styles.css"></templatestyles>
  30. "Route Renumbering: New Green Markers Will Replace Old Shields". California Highways and Public Works. 43 (3–4): 11–13. March–April 1964. ISSN 0008-1159. Retrieved June 10, 2011.<templatestyles src="Module:Citation/CS1/styles.css"></templatestyles>
  31. "New Signing Policy on U.S. Routes". California Highways and Public Works. 15 (10): 13, 28. October 1937. ISSN 0008-1159. Retrieved July 24, 2015 – via<templatestyles src="Module:Citation/CS1/styles.css"></templatestyles>

Further reading

  • Ingram, Tammy (2014). Dixie Highway: Road Building and the Making of the Modern South, 1900–1930. Chapel Hill: The University of North Carolina Press. ISBN 9781469615523.<templatestyles src="Module:Citation/CS1/styles.css"></templatestyles>

External links