 Mason–Dixon line

The Mason–Dixon line, also called the Mason and Dixon line or Mason's and Dixon's line, is a demarcation line between four U.S. states, forming part of the borders of Pennsylvania, Maryland, Delaware, and West Virginia (part of Virginia until 1863).It was surveyed between 1763 and 1767 by Charles Mason and Jeremiah Dixon in the resolution of a border dispute involving Maryland, Pennsylvania, and Delaware in Colonial America.