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 . 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. The dispute had its origins almost a century earlier in the somewhat confusing proprietary grants by King Charles II to Lord Baltimore and William Penn .

The Mason–Dixon line along the southern Pennsylvania border later became informally known as the boundary between the free states and the slave states. The Virginia portion was the northern border of the Confederacy. This usage especially came to prominence during the debate around the Missouri Compromise of 1820, when drawing boundaries between slave and free territory was an issue. It is still used today in the figurative sense of a line that separates the North and South politically and socially .

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