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 accessible by road only 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.
File:Ellis Island 1890 - 1935 NPS map.jpgState border of Ellis Island after New Jersey v. New York, 1998. Green is the area of the original natural island, part of New York City, New York, while the man-made rest of the island is part of Jersey City, New Jersey
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 the State of New York, 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 the State of New York.
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]
Arkansas has territory at Lua error: callParserFunction: function "#coordinates" was not found. across the Mississippi River on the northwest edge of Tennessee's Fort Pillow State Park, north of the Corona/Reverie, Tennessee irregularity (mentioned in the previous section).
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.
Louisiana and Mississippi also share 3 islands, at 31.754078 degrees north, 91.376270 west; 31.885015 north, 91.228315 west; as well as Middle Ground Island, Togo Island, Davis Island at Lua error: callParserFunction: function "#coordinates" was not found., an island at Lua error: callParserFunction: function "#coordinates" was not found., Stack Island at Lua error: callParserFunction: function "#coordinates" was not found., Cottonwood Island at Lua error: callParserFunction: function "#coordinates" was not found., and an island at Lua error: callParserFunction: function "#coordinates" was not found..
Mississippi, Louisiana, and Arkansas share an island at their tri-point at Lua error: callParserFunction: function "#coordinates" was not found..
Mississippi also owns 14 exclaves on the bank in Arkansas, while Arkansas has 15 of its own on Mississippi's side.
There are also many irregularities along the river between Arkansas/Tennessee, Missouri/Tennessee, and Missouri/Kentucky.
Boston Corner, New York, transferred from Massachusetts to New York because a mountain range made it difficult for Massachusetts authorities to police it
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.
