The Twelve-Mile Circle is an approximately circular arc which forms most of the boundary between

Pennsylvania Pennsylvania (; ( Pennsylvania Dutch: )), officially the Commonwealth of Pennsylvania, is a state spanning the Mid-Atlantic, Northeastern, Appalachian, and Great Lakes regions of the United States. It borders Delaware to its southeast, ...

and

Delaware Delaware ( ) is a state in the Mid-Atlantic region of the United States, bordering Maryland to its south and west; Pennsylvania to its north; and New Jersey and the Atlantic Ocean to its east. The state takes its name from the adjacent Del ...

. It is not actually a circle, but rather a combination of different circular arcs that have been feathered together. It is nominally a

circle A circle is a shape consisting of all points in a plane that are at a given distance from a given point, the centre. Equivalently, it is the curve traced out by a point that moves in a plane so that its distance from a given point is const ...

with a supposed—yet in fact only approximate and variable—

radius In classical geometry, a radius ( : radii) of a circle or sphere is any of the line segments from its center to its perimeter, and in more modern usage, it is also their length. The name comes from the latin ''radius'', meaning ray but also the ...

, centered in the town of New Castle, Delaware. In 1750, the center of the circle was fixed at the

cupola In architecture, a cupola () is a relatively small, most often dome-like, tall structure on top of a building. Often used to provide a lookout or to admit light and air, it usually crowns a larger roof or dome. The word derives, via Italian, from ...

of the courthouse in New Castle. The Twelve-Mile Circle continues into the

Delaware River The Delaware River is a major river in the Mid-Atlantic (United States), Mid-Atlantic region of the United States. From the meeting of its branches in Hancock (village), New York, Hancock, New York, the river flows for along the borders of N ...

. A small portion of the circle, known as the "Arc Line," also forms part of the Mason-Dixon line, separating Delaware and

Maryland Maryland ( ) is a state in the Mid-Atlantic region of the United States. It shares borders with Virginia, West Virginia, and the District of Columbia to its south and west; Pennsylvania to its north; and Delaware and the Atlantic Ocean to ...

. Two other small portions, although not actually demarcated until 1934, form parts of the boundary between the states of

and

New Jersey New Jersey is a state in the Mid-Atlantic and Northeastern regions of the United States. It is bordered on the north and east by the state of New York; on the east, southeast, and south by the Atlantic Ocean; on the west by the Delaware ...

. Although the Twelve-Mile Circle is often claimed to be the only territorial boundary in the United States that is a true

arc ARC may refer to: Business * Aircraft Radio Corporation, a major avionics manufacturer from the 1920s to the '50s * Airlines Reporting Corporation, an airline-owned company that provides ticket distribution, reporting, and settlement services * ...

, many cities in the South (such as

Plains, Georgia Plains is a town in Sumter County, Georgia, United States. The population was 776 at the 2010 census. It is part of the Americus Micropolitan Statistical Area. Plains is best known as the birthplace and home of Jimmy Carter, the 39th president o ...

) also have circular boundaries. Its existence dates back to 1681, when Charles II granted a deed to

William Penn William Penn ( – ) was an English writer and religious thinker belonging to the Religious Society of Friends (Quakers), and founder of the Province of Pennsylvania, a North American colony of England. He was an early advocate of democracy a ...

north of the already chartered Maryland. Charles created an exception, consisting of 12 miles around the town of New Castle and extending down the peninsula, as these lands were held by the

Duke of York Duke of York is a title of nobility in the Peerage of the United Kingdom. Since the 15th century, it has, when granted, usually been given to the second son of English (later British) monarchs. The equivalent title in the Scottish peerage was Du ...

, who had won them in conquest from the Dutch colonists. Later, on August 24, 1682, the Duke granted these lands to Penn as well, giving him: The boundaries of the circle were the focal point of the eighty-year Penn–Calvert Boundary Dispute. The fact that the circle extends into the Delaware River makes for an unusual territorial possession. Most territorial boundaries that follow watercourses split the water course between the two territories by one of two methods, either by the median line of the watercourse (the Grotian Method, after

Hugo Grotius Hugo Grotius (; 10 April 1583 – 28 August 1645), also known as Huig de Groot () and Hugo de Groot (), was a Dutch humanist, diplomat, lawyer, theologian, jurist, poet and playwright. A teenage intellectual prodigy, he was born in Delft ...

) or, more often, the center of the main flow channel, or thalweg (the lowest point in the stream channel). However, due to the text of the deed, within the Twelve-Mile Circle, all the Delaware River to the low-tide mark on the east (

) side is territory of the state of Delaware (a similar condition exists between the states of

Vermont Vermont () is a state in the northeast New England region of the United States. Vermont is bordered by the states of Massachusetts to the south, New Hampshire to the east, and New York to the west, and the Canadian province of Quebec to ...

and

New Hampshire New Hampshire is a U.S. state, state in the New England region of the northeastern United States. It is bordered by Massachusetts to the south, Vermont to the west, Maine and the Gulf of Maine to the east, and the Canadian province of Quebec t ...

, with the border being defined as the west bank of the

Connecticut River The Connecticut River is the longest river in the New England region of the United States, flowing roughly southward for through four states. It rises 300 yards (270 m) south of the U.S. border with Quebec, Canada, and discharges at Long Island ...

, leaving the river - and bridges - in sole possession of New Hampshire). New Jersey has often disputed this claim, as the rest of its territorial boundaries along the Delaware River are determined by the midline and thalweg methods. In 1813, Delaware's legislature passed an act deeding

Pea Patch Island Pea Patch Island is a small island, approximately 1 mi (1.6 km) long, in the U.S. state of Delaware, located in the mid channel of the Delaware River near its entrance into Delaware Bay. It is a low, marshy island, located in New Castle C ...

to the United States government, and in 1820 New Jersey disputed that they owned the island since it was primarily on the New Jersey side of the river. Attorney General William Wirt sided with Delaware. In the 1840s, the Pea Patch Island disagreement led to two conflicting circuit court decisions—the circuit of Delaware ruling that the entirety of the river (and its islands) belonged to Delaware, and the circuit in New Jersey ruling that the island had belonged to New Jersey, which had deeded it to Dr. Henry Gale, a citizen of New Jersey. At the recommendation of President

James K. Polk James Knox Polk (November 2, 1795 – June 15, 1849) was the 11th president of the United States, serving from 1845 to 1849. He previously was the 13th speaker of the House of Representatives (1835–1839) and ninth governor of Tennessee (183 ...

, the parties agreed to arbitration, which resulted in a confirmation of Delaware's claim. The arbitration did not ultimately resolve the dispute, and it has been brought to the

Supreme Court of the United States The Supreme Court of the United States (SCOTUS) is the highest court in the federal judiciary of the United States. It has ultimate appellate jurisdiction over all U.S. federal court cases, and over state court cases that involve a point o ...

on several occasions (all titled ''

New Jersey v. Delaware ''New Jersey v. Delaware'', 552 U.S. 597 (2008), is a United States Supreme Court case in which New Jersey sued Delaware, invoking the Supreme Court's original jurisdiction under (a), following Delaware's denial of oil company BP's petition to ...

''), most notably in 1877, 1934, 1935, and 2007. The court's opinion for the 1934 case contained an extensive history of the claims to this territory, and the 1935 opinion memorably enjoined New Jersey and Delaware from ever disputing their jurisdictions again. Regardless of the Supreme Court's admonition to the two states against further litigation on this subject, they were back before the court as late as November 2005, when New Jersey's desire to approve plans by BP to build a liquefied natural gas terminal along the New Jersey shore of the Delaware River fell afoul of Delaware's Coastal Zone Act. The court on January 23, 2006, appointed a special master to study the border dispute, and on March 21, 2008, it upheld his report, which largely supported Delaware's authority. Meanwhile, the Delaware House of Representatives considered a (symbolic) bill to call out the National Guard to safeguard the state's interests, while New Jersey legislators made comments about the battleship ''New Jersey'', moored upriver from the site.

Surveying the Circle

There are persistent rumors that

David Rittenhouse David Rittenhouse (April 8, 1732 – June 26, 1796) was an American astronomer, inventor, clockmaker, mathematician, surveyor, scientific instrument craftsman, and public official. Rittenhouse was a member of the American Philosophical Society ...

, the famous astronomer and instrument-maker of Pennsylvania, surveyed the circle around New Castle, but this is likely not correct. The circle was first laid out by surveyors named Taylor and Pierson in 1701. The 1813 "Memoirs of the life of David Rittenhouse" by William Barton surmises that Rittenhouse was involved in such a survey in 1763, based on a letter in which Rittenhouse mentions being paid "for my attendance at New Castle," but there is no clear record of what, exactly, Rittenhouse was paid for. His biographer, Brooke Hindle, guessed that Rittenhouse assisted with latitude or longitude calculations.Brooke Hindle, ''David Rittenhouse'', Princeton University Press, 1964, pp. 20–21.

References

{{Reflist, colwidth=35em Border irregularities of the United States Borders of Delaware Borders of Maryland Borders of New Jersey Borders of Pennsylvania Geography of Cecil County, Maryland Geography of Chester County, Pennsylvania Geography of Delaware County, Pennsylvania Geography of Maryland Geography of New Castle County, Delaware Geography of Salem County, New Jersey Internal territorial disputes of the United States

Surveying the Circle

See also

References