What Happened on October18th – The Mason-Dixon Line

On October 18, 1767, in order to settle a boundary dispute, Charles Mason and Jeremiah Dixon complete a survey of the boundary between the colonies of Pennsylvania and Maryland as well as areas that would eventually become the states of Delaware and West Virginia.

Hired by the Penn and Calvert families, Mason and Dixon, English surveyors had the task of settling a dispute over the boundary between the colonies owned by these families.

Map of the original Mason and Dixon Line

• Through 1760, there had been a lot of border violence between the colonies’ settlers.
• The British crown demanded that the parties involved hold to an agreement reached in 1732.
• Mason and Dixon were asked to determine the exact whereabouts of the boundary.
• What is now referred to as the Mason-Dixon line finally settled the boundary at a northern latitude of 39 degrees and 43 minutes.
• The line was marked using stones, with Pennsylvania’s crest on one side and Maryland’s on the other.

A “crownstone” boundary monument on the Mason–Dixon line. These markers were originally placed at every 5th mile along the line, ornamented with family coats of arms facing the state that they represented. The coat of arms of Maryland’s founding Calvert family is shown. On the other side are the arms of William Penn.

In 1763 when Mason and Dixon began, the colonists were in protest over the Proclamation of 1763 which prevented settlement of land beyond the Applachian Mountains.  The purpose was to prevent the angering of Native Americans.

When the line was concluded in 1767, the colonies were in a dispute with Parliament over the Townshend Acts, which were designed to raise revenue for the empire by taxing common imports including tea.

An American colonist reading with concern the royal proclamation of a tax on tea in the colonies, part of the Townshend Acts; political cartoon, Boston, 1767. Credit: Hulton Archive/Getty Images

The line would come into play twenty years later when in the late 1700s, the states south of the Mason-Dixon line would begin arguing for the perpetuation of slavery.  Those north of the line hoped to phase out human ownership. With the Missouri Compromise of 1820, this argument was set to rest for a time being.  Through this compromise, the nation accepted that the states south of the line are slave-holding and those north of the line are free. The compromise eventually failed.

The Missouri Compromise

One hundred years after Mason and Dixon began their survey for the boundary dispute, soldiers from opposite sides of the line fought against each other in the Battle of Gettysburg.

The Battle of Gettysburg by Currier and Ives

One hundred and one years after the line was completed, it was finally decreed in the United States that men of any complexion born within the nation had the rights of citizenship. This was through the ratification of the 14th Amendment.