Original explanation of US highway numbering, layout, and purpose reprinted from American Highways, Vol VI, No. 2, April 1927 :

For the Convenience of the Traveling Public a Limited System of State Roads Have Been Given Continuous Numbers Across the Country

For the past two years, the State highway departments of the Nation have been working on a plan, in cooperation with the Deparment of Agriculture, of designating certain through roads with numbers that would be carried continuous from coast to coast. Naturally this carries a limited mileage, but it is believed that the system approved takes care of the major part of interstate traffic.
The plan adopted provides that roads running north and south shall be odd numbers and roads running east and west, even numbers. Necessarily there must be some diagonal routes joining these odd and even routes. In laying out this system the highway officials felt that the simplicity of the plan adopted would be popular with the people, and in a large majority of the States, the numbers chosen have already been erected. The total mileage involved in the routes selected is 96,626 miles. This includes mileage through cities. In some instances, paticularly in mountainous country, it is necessary, for short distances, that a road carry two numbers; but in such cases both numbers will be erected on the same post and it will not be at all confusing to the traveling public. The design adopted is the commonly known United States shield outline, and this shield carries the route number, as well as the State name through which the road passes.
The following descriptions of these routes have been prepared after careful observation and approval of the State officials of each State. The roads designated by these numbers do not have any special preference over other roads on the Federal Aid Highway System, as far as construction and financing are concerned, but it is impossible to simplify interstate travel and have the entire Federal Aid System numbered according to this plan.

On November 11, 1926, AASHO accepted this list, and the individual states adopted the scheme at their own pace near that time. Some states had already posted routes during 1926 based on the 1925 plan, others waited until January 1927 to adopt these routes. In a few states, these were the only numbered state highways. The original list was point to point, listing cities, towns, and villages the road was to be routed through. As you can see below, split routes have been a fact since the plan was adopted, added as a compromise measure to get all the states to accept the scheme. All routes listed from north to south and / or east to west. Obvious typos in original list corrected (noted in the table in this color).

Symbology: (*) International boundary, (-) State line, (+) Road junction

US 120 Note: The eastern end of US 120 was truncated at Reading, PA in 1927 and replaced by an eastern leg of US 422. This may have been part of a plan to restore the 1925 plan US 22 Philadelphia - Cleveland connection. No one left alive recalls what was going through PennDOT's mind. There is some information on this at http://wwwcf.fhwa.dot.gov/infrastructure/us22.htm The western end of US 120 may have been extended to and retracted from Erie, PA over US 6 in the late 1920's, depending on which maps you believe.

Unifed System of Highways: One persistent rumor about the United States Numbered Highway System is that U.S. stands for Unified System. This is not true. US stands for United States, and was nearly U.S.A. - see this page for more details.

Sources:
American Highways, April, 1927 Vol. VI No. 2. (AASHO) c/o Donna Tamburelli, AASHTO (PDF available to my Yahoo Group)
United States Numbered Highways, Rec'd by U.S.D.A. B.P.R. May 26, 1927 (from BPR files) c/o Richard Weingroff, FHWA (PDF available to my Yahoo Group)
Official Paved Road Survey and Commercial Atlas, National Map Company, 1927
United States Road Atlases Rand McNally, 1926, 1927 and 1928

Route numbers absent from the numbering scheme as adopted November 11, 1926:
US 46 (US 40S in CO), US 62 (US 60 in KY+MO), US 109 (US 9E in NY), US 160 (US 166), US 250 (US 50S in KS), US 260 (US 266), US 280 (US 89 in AZ), US 301 (US 17 in VA), US 360 (US 366), US 380 (US 89 in AZ), US 460 {aka US 466} (US 85 in NM), US 560 (US 666), US 630 (UT)

By 1928: US 6 was one route, US 6N was in NY on the old route of US 6 (now US 209), US 19 was one route, US 164 was in OK and TX, US 227 was in KY, US 422 (East leg) and US 611 were in PA, and US 630 was in ID and OR. US 622 and US 711 had came and went in PA, and US 313 may have been used .

The 1932 US Numbered Highway list, based on a AAA US map. Not even six years and major changes already (Text format).

USDA Bureau of Public Roads 1925 Plan : The original plan, without any split or hyphenated routes. Based on the October 30, 1925 report approved by the US Secretary of Agriculture on November 18, 1925.

U.S. Highways: From US 1 to (US 830) - Back to the index.

US Numbered Highways of 1956: This table shows the US highway system at its zenith, just before the creation of the Interstate system. Jump ahead in time 29 years and about 20 miles per hour faster than the above list (Based heavily on a AAA USA map).

Last update to this page on Monday, February 28, 2005.

Page maintained by Robert V. Droz
E-mail me with any comments or requests for more details on specific roads.
This web page created June 29, 1998.