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.
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 counties, the United States operates a military base in Cuba, Guantanamo Bay.
The status of Cubans who illegally cross the Straits into the United States is determined by the wet feet dry feet policy. This means that a Cuban captured on US land may stay in the country, but a Cuban found at sea will be returned to Cuba.
Other irregularities involving the Mississippi River:
- Arkansas has territory at Fort Pillow State Park, north of the Corona/Reverie, Tennessee irregularity (mentioned in the previous section). across the Mississippi River on the northwest edge of Tennessee's
- Illinois' 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.
Separated by water other than the Mississippi River:
- Delaware has land on the New Jersey side of Delaware Bay at Fort Mott and near the Salem Nuclear Power Plant in Salem County. At that point, the border runs along New Jersey's mean low tide mark. Thus when the spoils from the navigational dredging of the Bay were dumped alongside Fort Mott and the Salem plant excavations nearby, both sites became part of New Castle County, Delaware.
- Iowa's city of Carter Lake on the Nebraska side of the Missouri River.
- Several small areas of western Kentucky lie north of the Ohio River on what is otherwise the Indiana side, including one area south of Evansville, Indiana that accommodates a horse racing track.
- Turtle Island, Michigan/Ohio
- Missouri's Rosecrans Memorial Airport, the airport for St. Joseph, is on the Kansas side of the Missouri River.
- Several portions of Nebraska lie east of the Missouri River, mainly due to flooding and changes in the river's path:
- DeSoto National Wildlife Refuge near Blair, which borders Iowa. A portion of Iowa is also on the Nebraska side in the same area.
- McKissick Island near Peru, which borders Missouri.
- A section of land that borders Iowa, Sloan.
- Onawa Materials Yard Wildlife Area and Middle Decatur Bend State Wildlife Management Area near Onawa, Iowa.
- The Eastern Shore of Virginia is separated by the Chesapeake Bay from the rest of the Commonwealth.
- The Delaware Wedge adjacent to Maryland and Pennsylvania
- The Erie Triangle.
- Michigan's Lost Peninsula Marina and neighboring Erie Township north of Toledo and Washington Township, Lucas County, Ohio; resulting from Toledo War border realignment.
- Massachusetts' Southwick Jog.
- Missouri's Bootheel.
- 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.
Highway system irregularities
- Oklahoma State Highway 20 forms a concurrency with Arkansas Highway 43 between Maysville, Arkansas and the Missouri state line, where AR-43 becomes Missouri Highway 43.
- Interstate 24 briefly enters Georgia for a few miles but comes back into Tennessee, and retains Tennessee exit numbers, but not Tennessee mile markers.
- Minnesota State Highway 23 enters Wisconsin near Duluth for half a mile.
- Interstate 684, otherwise in New York, takes a shortcut across the northwest corner of the Connecticut Panhandle without any exits or signage save a standard Connecticut sign welcoming travelers to Greenwich.
- Interstate 86, formerly NY 17, drops just south of the Pennsylvania state line for two miles between Waverly and Sayre. The crossing is indicated by signs in both directions, but the New York signage and exit numbering remain (prior to being converted to an interstate, Route 17's sequential exit numbering began at its Pennsylvania terminus and continued into New York, one of the few highways in the U.S. where this was so; however it is not uncommon for state highways to retain their route numbers when they change state highway shields at the border).
- New York State Route 120A runs along the Connecticut state line for much of its length, apart from 3.6 miles that enter the state, yet retains its New York signage and is still maintained by the New York State Department of Transportation.
- Montana State Highway 43 runs for approximately one mile inside Idaho, between Chief Joseph Pass and Lost Trail Pass. It crosses into Montana again just yards from its junction with US 93.
- The Woodrow Wilson Bridge carries I-95 and I-495 (the Capitol Beltway) across the Potomac River south of the District of Columbia. It connects Maryland on the east shore of the river with Virginia on the west shore. However, a few hundred feet of roadway close to the Virginia side crosses the southernmost point of the District of Columbia and thus is in neither Maryland nor Virginia.
Some highways are not connected to the rest of their nominal highway systems:
- In addition to Alaska and Hawaii being separated from the Lower 48, each has road systems isolated from each other. Alaska Route 7 and the other roads near Juneau, Alaska remain separated by ferry from other road systems.
- Iowa Highway 165 in Carter Lake, Iowa, is the only state highway in Iowa which is entirely west of the Missouri River. The highway is the middle span of the Omaha, Nebraska road named Abbott Drive, and is not directly connected to any other street. The rest of Carter Lake is a separate street system exclave accessible only from Locust Street or Avenue H in Omaha.
- M-185 is a state highway in Michigan. Like the rest of Mackinac Island, M-185 is prohibited to motor vehicles except for emergency vehicles.
- In Atchison County, Missouri, Missouri supplemental route V is separated from the rest of Missouri's highway system. It connects only to roads in Fremont County, Iowa. This is due to lying northwest of the Nishnabotna River.
- New York State Route 171, near Utica, does not intersect any other state highways (it once did, with NY 5S, but a realignment of that route took it away from the one intersection that NY 171 had).
- New Jersey Route 324 is an isolated route in Logan Township, New Jersey that connects to the former docks of a ferry on the Delaware River carrying US Route 322 to Chester, Pennsylvania. The ferry was replaced by the Commodore Barry Bridge in 1974. Route 324 used to connect to New Jersey Route 44 at its eastern end prior to a realignment.
- A bridge connecting to Pond Eddy, Pennsylvania across the Delaware River to New York State is owned by Pennsylvania, despite having no connection to the rest of Pennsylvania's road network. One must use New York Route 97 to cross back over the river at Narrowsburg, New York or Port Jervis, New York, a distance of approximately 14 miles (23 km). When the original bridge needed replacement, Pennsylvania had considered buying out the property owners and demolishing the town and the bridge. (Bridges over the Delaware River between the two states are maintained by a joint commission operated by the transportation departments of both states.)