The boundary known as the "Mason-Dixon Line" is traditionally considered the dividing line between slave states and free states in the United States prior to the Civil War. It runs between Pennsylvania and Maryland and was surveyed in the 1760s by Charles Mason and Jeremiah Dixon to resolve border disputes. Over time, this line emerged as a cultural and political symbol, representing the differences between the North and South regarding slavery. Today, it marks a historical division and continues to be referenced in discussions about America's past and regional identities.