The Mason-Dixon Line separates Pennsylvania, Maryland, Delaware and West Virginia. Charles Mason and Jeremiah Dixon were commissioned to survey the line between 1763 and 1767 to resolve an ongoing border dispute between British colonies in colonial America.
The Mason-Dixon Line became widely known as the symbolic division between the Northern and Southern states during America's Civil War. In short, it divided slave states from non-slave states. In spite of an arduous and contentious history, the Mason-Dixon Line still exists in 2014. It was last resurveyed in 1902 and, notwithstanding some minor adjustments, the line was found to be remarkably accurate.