Mason-Dixon Line

   It is generally understood that the Mason and Dixon line divides the North from the South in the Atlantic region of the United States, and it is used as a figure of speech when discussing regional custom and viewpoints of all sorts. Below the Mason-Dixon line is considered the South, and the phrase during the Civil War was used to mean the difference between free and slave states.

   The story behind this "line" began during colonial times when the Penns of Pennsylvania and the Calverts of Maryland had a dispute over their land grants. The matter was eventually taken to a London court and, in 1760, a compromise was reached. The compromise consisted simply of letting two English astronomers, acting as surveyors, mark the boundaries of the two grants. The names of these astronomer-surveyors were Charles Mason and Jeremiah Dixon.

   Mason and Dixon decided on an ambitious program. They imported from England milestones bearing the arms of the Penns on one side and of the Calverts on the other. The markers were placed every five miles, but the task was just too much for them. By 1767 they had placed the markers—had run the line—244 miles. The survey was completed by others for Maryland in 1773, all the way to its western border. The southern boundary of Pennsylvania was completed six years later. The line was fixed at 39° 43' 26.3° N.