Secession in the United States

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In the context of the United States, secession primarily refers to the voluntary withdrawal of one or more states from the Union that constitutes the United States; but may loosely refer to leaving a state or territory to form a separate territory or new state, or to the severing of an area from a city or county within a state. Advocates for secession are called disunionists by their contemporaries in various historical documents.

Threats and aspirations to secede from the United States, or arguments justifying secession, have been a feature of the country's politics almost since its birth. Some have argued for secession as a constitutional right and others as from a natural right of revolution. In Texas v. White (1869), the Supreme Court ruled unilateral secession unconstitutional, while commenting that revolution or consent of the states could lead to a successful secession.

The most serious attempt at secession was advanced in the years 1860 and 1861 as 11 Southern states each declared secession from the United States, and joined to form the Confederate States of America, a procedure and body that the government of the United States refused to accept. The movement collapsed in 1865 with the defeat of Confederate forces by Union armies in the American Civil War.^[1]

In the history of the United States, the only territories to have been withdrawn from the country are the small portions of the Louisiana Purchase north of the 49th parallel north, established as the U.S.–British (now Canadian) border by the Treaty of 1818; and the territory of the Commonwealth of the Philippines, which became independent after the Treaty of Manila. The former is today part of Canada, while the latter corresponds to the Republic of the Philippines.

Boundaries of U.S. territories, such as the Nebraska Territory, were not defined precisely. The boundaries of each new state are set in the document admitting the former territory to the Union as a state, which Congress must approve. There are three instances in U.S. history in which a portion of a state successfully seceded to create a new state: Kentucky which separated from Virginia in 1792, Maine separating from Massachusetts in 1820, and West Virginia, which also separated from Virginia, in 1863.^[2][3]