Mason-Dixon Line

Etymology
Named after English astronomers (1728–1786) and  (1733–1779).

Proper noun

 * 1)  The boundary line between Pennsylvania and Maryland, as run (1764–1767) by  and, that, before abolition, defined part of the northern boundary of states in which slavery was permitted.
 * 2) The boundary between the free and slave states at the time of the American Civil War, or between states with different segregationist policies in the Jim Crow era.
 * 1) The boundary between the free and slave states at the time of the American Civil War, or between states with different segregationist policies in the Jim Crow era.
 * 1) The boundary between the free and slave states at the time of the American Civil War, or between states with different segregationist policies in the Jim Crow era.
 * 1) The boundary between the free and slave states at the time of the American Civil War, or between states with different segregationist policies in the Jim Crow era.

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