Border irregularities of the United States

Border irregularities of the United States, particularly panhandles, territory effectively an exclave because of water, and highway incursions into other states, are not uncommon. Often they are a result of geometric borders not following geological features. The United States has a handful of these.

Contents 1 Geographic irregularities 2 Highway system irregularities 2.1 Highway exclaves 3 References

Geographic irregularities

Separated from rest of territory by Mississippi River or other river changes from the massive 1812 New Madrid earthquake:

• Tennessee's Reverie and Corona, located in Tipton County north-northwest of Memphis.^[1]
• (Some of those below may belong in this category)

Other irregularity involving the Mississippi River:

• Arkansas has territory at across the Mississippi River on the northwest edge of Tennessee's Fort Pillow State Park, north of the Corona/Reverie, Tennessee irregularity below.
• Illinois' Kaskaskia 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:

• Delaware has land on the New Jersey side of the Delaware Bay at Fort Mott and near the Salem Nuclear Power Plant in Salem County. At that point in the Delaware Bay the border runs along New Jersey's mean low tide mark. Thus when navigational dredging from the Bay was dumped alongside Fort Mott and the Salem plant excavations used as landfill nearby, both sites became part of New Castle County in the state of 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.
• Michigan's Upper Peninsula.
• Minnesota's Northwest Angle and Elm Point.
• Missouri's Rosecrans Memorial Airport, the airport for St. Joseph, is on the Kansas side of the Missouri River.
• Several separate portions of Nebraska lie east of the Missouri River, most of which was caused 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 Missouri side of the river in the same area.
  • McKissick Island near Peru, which borders Missouri.
  • A section of land that borders an area near Sloan, Iowa.
  • Onawa Materials Yard Wildlife Area and Middle Decatur Bend State Wildlife Management Area near Onawa, Iowa.
• Vermont's Alburgh.
• The Eastern Shore of Virginia is separated by the Chesapeake Bay from the rest of the state.
• Washington's Point Roberts.

Other irregularities:

• The Delaware Wedge adjacent to Maryland and Pennsylvania^[2]
• The Erie Triangle
• Michigan's Lost Peninsula Marina and exclaves next to it in Erie Township, Michigan north of Toledo and Washington Township, Lucas County, Ohio; resulting from Toledo War border realignment.
• Massachusetts' Southwick Jog.
• Missouri's Bootheel.

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.
• 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, but for 3.6 miles enters that state entirely, 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.

Highway exclaves

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.

References