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 such as changes in the course of a river that previously marked a border.
There are several exclaves between the United States and Canada, including the entire state of
Alaska (though the state can still be accessed by sea from the United States, except the small settlement of
Hyder which is only accessible by road from
British Columbia). Other exclaves include
Akwesasne, the
Northwest Angle,
Point Roberts, and Seaway Island.
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 is Canadian is surrounded by sea territory that the U.S. has declared to be American.
Another disputed area is the Grey Zone, including
Machias Seal Island, in the Gulf of Maine.
East Richford Slide Road in the U.S. state of
Vermont crosses into the Canadian province of
Québec for a distance of approximately 330 feet (100 m) before returning to the United States.[7]
In
Texas and
Mexico, shifts in the course of the lower Rio Grande have created numerous
bancos. 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 exclaves of the state of
Texas now lying on the southern side of the river, as well as 68 such exclaves of Mexico on the northern side of the river.
The legal status of the
U.S.-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.
Parts of Delaware exist within NJ - Delaware and New Jersey are largely divided by the Delaware River and Delaware Bay. However, the two states also share two land borders. For example, in Pennsville, NJ, a section of land that is mainly marsh area, (approximately 1.7 miles (2.7 km) in length and 0.6 miles (0.97 km) wide) is actually owned by Delaware.[9]
Iowa's city of
Carter Lake on the Nebraska side of the Missouri River, since 1877 when a flood redirected the Missouri River and formed an
oxbow lake and a section of Iowa trapped on the other side of the river. In particular, people driving between
Omaha and
Eppley Airport pass "Welcome to Iowa" signs in both directions.
Onawa Materials Yard Wildlife Area and Middle Decatur Bend State Wildlife Management Area near
Onawa, Iowa.
The mainland portion of
Newport County, Rhode Island is separated from the rest of the state by the delta of the
Taunton River. The only land connection is through
Massachusetts, but it is possible to access these communities by bridge without leaving Rhode Island.
The above-water portion of
Liberty Island is part of
New York State, but being located in
New York Bay, is entirely surrounded by the waters of
New Jersey. Ellis Island is also in the waters of New Jersey, but the naturally formed part of the island belongs to New York, while the artificial infill portion surrounding it belongs to New Jersey. The original land area of Ellis Island is a true exclave of New York State.
New Jersey and New York share
Shooter's Island, a bird sanctuary located in the south end of
Newark Bay off the north shore of
Staten Island. (The small portion in New Jersey is further divided between two counties.)
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.[11]
Illinois's
Kaskaskia, Missouri's
Grand Tower Island and other Illinois and Missouri territory on each other's side of the Mississippi River.
The
Kentucky Bend between Missouri and Tennessee. The
Royal Colonial Boundary of 1665 selected an arbitrary line of latitude that, extended westward, isolated a bulb-shaped section of Kentucky from the rest of the state, accessible only through Tennessee.
The state of
Mississippi controls at least 11 exclaves on the west bank of the Mississippi River in
Louisiana, while Louisiana owns 8 exclaves on Mississippi's side.
Boston Corner, New York, transferred from Massachusetts to New York because a mountain range made it difficult for Massachusetts authorities to police it
Municipal and borough boundaries
Marble Hill remains legally part of the borough of
Manhattan, even though it was separated from the island of Manhattan by construction of the Harlem Ship Canal in 1895 and then connected to the mainland and the
Bronx in 1914.
^Davidson, George (1903).
The Alaska Boundary. San Francisco: Alaska Packers Association. pp.
79–81, 129–134, 177–179, 229.
^"Chapter 1: Eastern Maine". United Divide: A Linear Portrait of the USA/Canada Border. The Center for Land Use Interpretation. Winter 2015. Archived from
the original on 2018-12-10. Retrieved 2018-10-01.