A Plan of the West Line or Parallel of Latitude


This map shows the original Mason-Dixon Line, traditionally thought of as the divide between North and South in the United States and, before the Civil War, between the slaveholding and non-slaveholding states. In the 1700s, a boundary dispute arose between the British colonies of Maryland and Pennsylvania. They agreed to resolve the dispute by having two English astronomers, Charles Mason (1728–86) and Jeremiah Dixon (1733–79), survey the border. Mason and Dixon completed their survey in 1767 and set up milestones to mark the line. This map was made by Mason and published in Philadelphia in 1768. The Mason-Dixon Line was resurveyed in 1849, 1900, and, most recently, the 1960s and has proven to be highly accurate. Today, the line is set at 39°43’19.521” north latitude. It forms the boundary between Pennsylvania and Maryland, between Pennsylvania and part of West Virginia, and the north–south boundary between Maryland and Delaware. The origin of “Dixie,” the traditional nickname for the American South and the unofficial national anthem of the Confederacy during the Civil War, is obscure, but one theory holds that the name derives from Jeremiah Dixon.

Last updated: May 24, 2017