Border irregularities of the United States

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Border irregularities of the United States, particularly panhandles and highway incursions into other jurisdictions, are shown here. Often they are a result of borders which do not conform to geological features.



There are several exclaves between the United States and Canada, including the entire state of Alaska. Other exclaves include the Northwest Angle, Point Roberts and Akwesasne.

The status of the waters around Nunez Rocks is disputed. Nunez Rocks is a low-tide elevation ("bare at half-tide"[1]) area (LTE) that is south of a line known as the "A-B" Line,[2] which was defined in a 1903 arbitration decision on the Alaska–Canada boundary.[3] The court specified the initial boundary point (Point "A") at the northern end of Dixon Entrance[4] and Point "B" 72 nautical miles (83 mi; 133 km) to the east.[5] Canada relies on the "A-B" Line as rendering nearly all of Dixon Entrance as Canadian internal waters. The U.S. does not recognize the "A-B" Line as an official boundary, instead regarding it as allocating sovereignty over the land masses within the Dixon Entrance,[2] with Canada's land south of the line. The U.S. regards the waters as subject to international marine law, and in 1977 it defined an equidistant territorial sea throughout Dixon Entrance.[2] This territory, which surrounds Nunez Rocks, extends south of the "A-B" line for the most part.[2] The United States has not ratified the Law of the Sea Treaty, although it adheres to most of its principles as customary international law. Under the treaty, LTEs may be used as basepoints for a territorial sea, and the U.S. uses Nunez Rocks as a basepoint. As a non-signatory, however, there is nothing preventing the U.S. from claiming areas beyond the scope of the Law of the Sea Treaty. The fact remains that, for about half of each day, above-water territory that Canada regards as Canadian is surrounded by sea territory that the U.S. has declared to be American.


In Texas and Mexico, shifts in the course of the lower Rio Grande have created numerous pene-exclaves. Under the Boundary Treaty of 1970 and earlier treaties, the United States and Mexico have maintained the actual course of the river as the international boundary, but both must approve proposed changes. From 1989 to 2009, there were 128 locations where the river changed course, causing land that had been on one side of the river to then occupy the opposite bank. Until the boundary is officially changed, there are 60 small pene-exclaves of the state of Texas now lying on the southern side of the river, as well as 68 such pene-exclaves of Mexico on the northern side of the river.


The legal status of the US-Russian border is unclear. The United States Senate ratified a treaty setting the boundary with the Soviet Union in 1991. However, shortly after, the Soviet Union collapsed, and the Russian parliament never voted on the treaty.


The boundary between the United States and Cuba is a maritime boundary along the Straits of Florida. Despite tense relations between the countries, the United States operates a military base in Cuba, Guantanamo Bay.


Separated by changes in the Mississippi River during the 1812 New Madrid earthquake or other river changes:

  • Over a period of about 24 hours on 7 March 1876, the Mississippi River abandoned its former channel that defined the Tennessee-Arkansas border, and established a new channel east of Tennessee's Reverie and Corona, located in Tipton County north-northwest of Memphis.[6]

Other irregularities involving the Mississippi River:

Separated by water other than the Mississippi River:

Other irregularities:

Highway irregularity signage in New York
A white on green sign saying "State border". Behind it in the distance is a standard U.S. freeway exit sign.
Sign on Pennsylvania border on NY Route 17
Three signs along a busy freeway. The one at the bottom says "Entering Greenwich Connecticut". The one above it has "Litter Removal" on it. The last one, at the top, is irregularly shaped with the number 684
State border sign on I-684

Highway system irregularities[edit]

Highway exclaves[edit]

Some highways are not connected to the rest of their nominal highway systems:


  1. ^ U.S. National Geodetic Survey. "NOAA Shoreline Data Explorer". Retrieved 2015-04-10. 
  2. ^ a b c d Gray, David H. (Autumn 1997). "Canada's Unresolved Maritime Boundaries" (PDF). IBRU Boundary and Security Bulletin. p. 61. Retrieved 2015-03-21. 
  3. ^ "International Boundary Commission definition of the Canada/US boundary in the NAD83 CSRS reference frame". Retrieved 2015-03-21. 
  4. ^ White, James (1914). Boundary Disputes and Treaties. Toronto: Glasgow, Brook & Company. pp. 936–958. 
  5. ^ Davidson, George (1903). The Alaska Boundary. San Francisco: Alaska Packers Association. pp. 79–81, 129–134, 177–179, 229. 
  6. ^ "Tipton". Tennessee History for Kids. Nashville, Tennessee: Tennessee History for Kids. 2010-01-18. Retrieved 2010-04-20. 
  7. ^ Lewis and Clark and Julia Butler Hansen National Wildlife Refuges Draft CCP/EIS Chapter 2. Alternatives, Goals, Objectives, and Strategies (PDF). Washington, DC: United States Fish and Wildlife Service. pp. 2–27. Retrieved 2016-04-20. 
  8. ^ .Whong, Christopher M. (2000-12-11). "The Boundary Disputes of Colonial Maryland". Baltimore, Maryland. Retrieved 2010-04-20.