The system of United States Numbered Highways (often called U.S. Routes or U.S. Highways) is an integrated system of roads and highways in the United States numbered within a nationwide grid. As these highways were coordinated among the states, they are infrequently referred to as Federal Highways, but they have always been maintained by state or local governments since their initial designation in 1926. There has never been any de jure federal funding difference between these routes and any other state highways. The numbers and locations are coordinated by the American Association of State Highway and Transportation Officials (AASHTO), in which the only federal involvement is a non-voting seat for the United States Department of Transportation.The Interstate Highway System has largely replaced the U.S. Highways for through traffic, though many important regional connections are still made by U.S. Highways, and new routes are still being added.
The very similar Trans-Canada Highway is often considered the Canadian counterpart to the U.S. Highway System, although it is much more limited in scope.
See also: List of United States Numbered Highways. In general, U.S. Highways do not have a minimum design standard, unlike the later Interstate Highways, and are not usually built to freeway standards, although some stretches of U.S. Highways do meet those standards. Many are the main streets of the cities and towns through which they run. However, new additions to the system must "substantially meet the current AASHTO design standards".
Except for toll bridges and tunnels, very few U.S. Highways 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." However, none of the four toll roads in the system follow this:
The two-digit U.S. Routes follow a simple grid, in which odd-numbered routes run generally north to south and even-numbered routes run generally east to west. (U.S. Route 101 is considered two-digit, its first 'digit' being ten.) Numbers generally increase from 1 in the east to 101 in the west and 2 in the north to 98 in the south. Numbers ending in zero or one (and U.S. Route 2 ), and to a lesser extent in five, were considered main routes in the early numbering, but extensions and truncations have made this distinction largely meaningless; for instance, U.S. Route 6 was until 1964 the longest route (that distinction now belongs to U.S. Route 20). The Interstate System grid, which increases from west to east and south to north, is intentionally opposite from the U.S. grid, to keep identically numbered routes apart and keeping them from being confused.
Three-digit numbers are assigned to spurs of two-digit routes. For instance, U.S. Route 201 splits from U.S. Route 1 at Brunswick, Maine and runs north to Canada. Not all spurs travel in the same direction as their "parents"; some are only connected to their "parents" 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, U.S. Route 60 junctioned, from east to west, U.S. Route 160 in Missouri, U.S. Route 260 in Oklahoma, U.S. Route 360 in Texas, and U.S. Route 460 and U.S. Route 560 in New Mexico. As with the two-digit routes, three-digit routes have been added, removed, extended and shortened; the "parent-child" relationship is not always present. Several spurs of the decommissioned U.S. Route 66 still exist, and U.S. Route 191 travels from border to border, while U.S. Route 91 has been largely replaced by Interstate 15.
Several routes approved since 1980 do not follow the pattern:
In addition, U.S. Route 163, approved ca. 1971, is nowhere near U.S. Route 63. The short U.S. Route 57, approved ca. 1970, connects to Federal Highway 57 in Mexico, and lies west of former U.S. Route 81.
While AASHTO guidelines specifically prohibit Interstate Highways and U.S. Highways from sharing a number within the same state (which is why there are no Interstates 50 or 60), the initial Interstate numbering approved in 1958 violated this with Interstate 24 and U.S. Route 24 in Illinois and Interstate 40, Interstate 80, U.S. Route 40 and U.S. Route 80 in California. (US 40 and US 80 were removed from California in its 1964 renumbering.) Some recent and proposed Interstates, some of them out-of-place in the grid, also violate this: Interstate 41 and U.S. Route 41 in Wisconsin (which will run concurrently), Interstate 49 and U.S. Route 49 in Arkansas, Interstate 69 and U.S. Route 69 in Texas, and Interstate 74 and U.S. Route 74 in North Carolina (which will run concurrently).
See main article: List of divided U.S. Routes. Divided routes have been around since 1926, and designate roughly-equivalent splits of routes. For instance, U.S. Route 11 splits into U.S. Route 11E (east) and U.S. Route 11W (west) in Knoxville, Tennessee, and the routes rejoin in Bristol, Virginia. Occasionally only one of the two routes is suffixed; U.S. Route 6N in Pennsylvania does not rejoin U.S. Route 6 at its west end. AASHTO has been trying to eliminate these since 1934; its current policy is to deny approval of new ones and to eliminate existing ones "as rapidly as the State Highway Department and the Standing Committee on Highways can reach agreement with reference thereto".
See main article: List of bannered U.S. Routes. Special routes—those with a banner such as alternate or bypass—are also managed by AASHTO. These are sometimes designated with lettered suffixes, like A for alternate or B for business.
The official route log, last published by AASHTO in 1989, has been named United States Numbered Highways since its initial publication in 1926. In the 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, at least 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. The use of U.S. Route or U.S. Highway on a local level depends on the state.
See main article: Auto trail. In the early 1910s, auto trail organizations - most prominently the Lincoln Highway - began to spring up, marking and promoting routes for 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.
Wisconsin was the first state in the U.S. to number its highways, erecting signs in May 1918. Other states soon followed, and the New England states got together in 1922 to establish the six-state New England Interstate Routes.
Behind the scenes, the federal aid program had begun with the passage of the Federal-Aid Highway 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 3/7 had to be "interstate in character". Identification of these main roads was completed in 1923.
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.
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 name - U.S. Highway - was adopted. It was also 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 adopted, based on the shield found on the Great Seal of the United States.
Opposition soon formed from the auto trail associations, who 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. The auto trail associations were not able to address the meetings, but as a compromise did talk with Joint Board members, and came out with general agreement with their plans. The tentative system added up to 81000 miles (130000 km), 2.8% of the public road mileage at the time.
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 of only 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. The shield, with few modifications from the original sketch, was adopted at that meeting, as was 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".
After working with states to get their approval, the system had expanded to 75800 miles (122000 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 they spurred from. The five-man committee met September 25, and submitted the final report to the Joint Board secretary on October 26. The board sent the report to the Secretary of Agriculture of October 30, and he approved it November 18, 1925.
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The new system was both praised and criticized by local newspapers, often depending on whether that city ended up on a major route. While the Lincoln Highway Association understood and supported the plan, partly because they were assured of getting the U.S. Route 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.
In the Northeast, New York still wanted fewer routes, and Pennsylvania, which had been absent from 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 U.S. Route 220 still ends near the state line, and now it ends at an intersection with future Interstate 86.) The indirect nature of U.S. Route 20, passing through Yellowstone National Park, led Idaho and Oregon to request that U.S. Route 30 be swapped with US 20 to the Pacific coast.
Many local disputes centered on the choice between two roughly-equal parallel routes, often competing auto trails. At their January meeting, AASHO approved the first two of many split routes (specifically U.S. Route 40 between Manhattan, KS and Limon, CO and U.S. Route 50 between Baldwin City, KS and Garden City, KS). 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.
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 east from Los Angeles to Oklahoma City, but then angled sharply to the northeast, running more north-south than east-west in Illinois. Kentucky strongly objected to this, as it had been left off any of the major east-west routes, instead receiving the U.S. Route 62 designation. This, along with the part of U.S. Route 52 east of Ashland, KY, was assigned the U.S. Route 60 number in January 1926, while US 62 was given 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, MO into US 60E and US 60N, but both sides objected. The final solution resulted in the assignment of U.S. Route 66, which did not end in zero, but was still seen as a nice round number.
With 32 states already marking their routes, the plan was approved by AASHO on November 11, 1926. This plan included a number of directionally-split routes, several discontinuous routes (including U.S. Route 6, U.S. Route 19 and U.S. Route 50), and some termini at state lines. Major numbering changes had been made in Pennsylvania by the publishing of the first route log in April 1927, in order to align the routes to the auto trails, and U.S. Route 15 had been extended across Virginia. Further modifications and additions were made in the next few years.
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 saw a numbered highway system as cold and heartless compared to the more colorful names 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?" Ernest McGaffey was quoted as saying, "Logarithms will take the place of legends, and 'hokum' for history."
In 1934, AASHO attempted 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 U.S. Route 37 in one case. AASHO described this in the October 1934 issue of American Highways:
When the U.S. numbered system was started in 1925, a few optional routings were established which were designated with the affix: "North," "South," "East," or "West." This procedure has never been to the traveling public, and while there are but a few roads numbered in this manner in the entire country, it is believed that they should be eliminated wherever possible, by the absorption of one of the optional routes into another route.
Wherever these optional routes are not of sufficient length for them to become a part of another numbered road, it is proposed to give the regular number to the older or shortest route, and the other route is to bear the same number with a standard strip above the shield carrying the word "Alternate."
Some states accepted this, and marked the routes as requested. But several states refused, including California, Mississippi, Nebraska, Oregon and Tennessee. In 1952 AASHO recognized the splits in U.S. Route 11, U.S. Route 19, U.S. Route 25, U.S. Route 31, U.S. Route 45, U.S. Route 49, U.S. Route 73 and U.S. Route 99. 
General expansion and the occasional elimination continued to occur through the years. One of the more interesting cases was the proposed extension of U.S. Route 97 to Alaska along the Alaska Highway, cancelled because the Yukon Territory refused to renumber its section as 97. For the most part, the U.S. Highways remained the primary method of intercity travel; the main exceptions were toll roads such as the Pennsylvania Turnpike and parkways such as the Merritt Parkway. Many of the first high-speed roads were U.S. Highways: the Gulf Freeway carried U.S. Route 75, the Pasadena Freeway carried U.S. Route 66, and the Pulaski Skyway carried U.S. Route 1 and U.S. Route 9.
The Federal-Aid Highway Act of 1956 appropriated funding for the Interstate Highway System, a vast network of freeways across the country. By 1957, AASHTO had decided to assign a new grid - opposing the U.S. Highway grid - to the new routes. Though the Interstate numbers were to supplement, rather than replace, the U.S. Highway numbers, in many cases (especially in the West) they were routed along the new Interstates as there was no need for the states to maintain two parallel routes through sparsely populated territory. Major decommissioning began with California's 1964 renumbering, and the 1985 removal of U.S. Route 66 is often seen as the end of an era.
AASHTO has recognized that state highways are now symbols of good roads as the U.S. Routes once were. Thus it has acted to rationalize the system by eliminating all single-state routes 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".