United States Numbered Highway System (English Wikipedia)

Duncan, Dayton; Burns, Ken (2003). Horatio's Drive: America's First Road Trip (1st ed.). New York: Alfred A. Knopf. p. ix. ISBN 0-375-41536-X.
"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.
"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 Archive.org.

broermapsonline.org

Rand McNally (1946). Road Atlas (Map). Scale not given. Chicago: Rand McNally. p. 42. New York and Vicinity inset. Archived from the original on July 25, 2011. Retrieved June 9, 2009.

cahighways.org

Correspondence between the Division of Highways and American Association of State Highway Officials, transcribed at "State Route 66". California Highways. Retrieved June 10, 2011.^{[self-published source?]}

coloradodot.info

apps.coloradodot.info

Colorado Department of Transportation. "Segment Descriptions for Highway 006". Colorado Department of Transportation. Archived from the original on May 26, 2012. Retrieved June 10, 2011.

deldot.gov

Delaware Department of Transportation (2006). "2006 Traffic Count and Mileage Report" (PDF). Delaware Department of Transportation. Archived from the original (PDF) on March 18, 2009. Retrieved June 10, 2011.

dot.gov

fhwa.dot.gov

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.
Federal Highway Administration (December 4, 2012). "November 13". Highway History. Federal Highway Administration. Retrieved August 18, 2013.
Federal Highway Administration (n.d.). "Interstate FAQ". Federal Highway Administration. Archived from the original on May 7, 2013. Retrieved June 26, 2009. Proposed I-41 in Wisconsin and partly completed I-74 in North Carolina respectively are possible and current exceptions not adhering to the guideline. It is not known if the U.S. Highways with the same numbers will be retained in the states upon completion of the Interstate routes.
"Ask the Rambler: What Is The Longest Road in the United States?". Federal Highway Administration. April 7, 2011. Retrieved April 11, 2010.
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.
Weingroff, Richard F. (April 7, 2011). "US 22: The William Penn Highway". Highway History. Federal Highway Administration. Retrieved June 9, 2011.

mutcd.fhwa.dot.gov

Federal Highway Administration (2009). Manual on Uniform Traffic Control Devices (2009 ed.). Washington, D.C.: Federal Highway Administration. ISBN 9781615835171. Retrieved June 5, 2010.

google.com

Google searches on thomas.loc.gov for "United States Route", "U.S. Route", "United States Highway" and "U.S. Highway"

grmims.com

grmservices.grmims.com

"An Application From the State Highway Department of Texas For the Establishment of a U.S. Route (U.S. 57)". American Association of State Highway Officials. September 15, 1970. pp. 2–3. Retrieved March 14, 2023 – via AASHTO Route Numbering Archive.

texasfreeway.com

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.

transportation.org

route.transportation.org

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. Archived from the original (PDF) on January 1, 2014. Retrieved March 16, 2012.

cms.transportation.org

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. Archived from the original (PDF) on November 1, 2006. Retrieved January 23, 2008.

web.archive.org

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. Archived from the original (PDF) on January 1, 2014. Retrieved March 16, 2012.
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. Archived from the original (PDF) on November 1, 2006. Retrieved January 23, 2008.
Federal Highway Administration (n.d.). "Interstate FAQ". Federal Highway Administration. Archived from the original on May 7, 2013. Retrieved June 26, 2009. Proposed I-41 in Wisconsin and partly completed I-74 in North Carolina respectively are possible and current exceptions not adhering to the guideline. It is not known if the U.S. Highways with the same numbers will be retained in the states upon completion of the Interstate routes.
Delaware Department of Transportation (2006). "2006 Traffic Count and Mileage Report" (PDF). Delaware Department of Transportation. Archived from the original (PDF) on March 18, 2009. Retrieved June 10, 2011.
Colorado Department of Transportation. "Segment Descriptions for Highway 006". Colorado Department of Transportation. Archived from the original on May 26, 2012. Retrieved June 10, 2011.
Rand McNally (1946). Road Atlas (Map). Scale not given. Chicago: Rand McNally. p. 42. New York and Vicinity inset. Archived from the original on July 25, 2011. Retrieved June 9, 2009.

wikimedia.org

commons.wikimedia.org

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: United States Geological Survey. OCLC 32889555. Retrieved November 7, 2013 – via Wikimedia Commons.

wikipedia.org

en.wikipedia.org

As of 1989^[update].^[3]

wikisource.org

en.wikisource.org

Joint Board on Interstate Highways (1925). Report of Joint Board on Interstate Highways, October 30, 1925, Approved by the Secretary of Agriculture, November 18, 1925 (Report). Washington, DC: United States Department of Agriculture. OCLC 733875457, 55123355, 71026428. Retrieved November 14, 2017 – via Wikisource.

worldcat.org

Joint Board on Interstate Highways (1925). Report of Joint Board on Interstate Highways, October 30, 1925, Approved by the Secretary of Agriculture, November 18, 1925 (Report). Washington, DC: United States Department of Agriculture. OCLC 733875457, 55123355, 71026428. Retrieved November 14, 2017 – via Wikisource.
Esso & General Drafting (1966). United States Featuring the Interstate Highway System (Map). [c. 1:3,870,000]. Convent Station, NJ: General Drafting. OCLC 749860157.
American Association of State Highway Officials; Bureau of Public Roads (1961). Manual for Signing and Pavement for the National System of Interstate and Defense Highways (1961 ed.). Washington, D.C.: American Association of State Highway Officials. OCLC 43890586.
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: United States Geological Survey. OCLC 32889555. Retrieved November 7, 2013 – via Wikimedia Commons.
"United States Numbered Highways". American Highways. American Association of State Highway Officials. April 1927. ISSN 0002-8746.
"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.
"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 Archive.org.