Mason‐Dixon Line

Mason‐Dixon Line. The Mason‐Dixon Line initially established the boundary between Pennsylvania and Maryland, resolving a lengthy dispute between the Penn and Calvert families, proprietors of the respective colonies. Both families claimed land that included Philadelphia, while Pennsylvania claimed the so‐called lower counties that make up present‐day Delaware. The dispute produced armed conflicts over tax collection and occasional uprisings against one proprietary regime or the other. Under a 1760 agreement, the two families accepted a proposal for a survey to be conducted by a pair of English astronomers and surveyors, Charles Mason and Jeremiah Dixon. The agreement required the use of a complex series of calculations incorporating the most advanced surveying methods of the day. Mason and Dixon conducted their survey between 1763 and 1767, encountering rugged terrain, political intrigues, and hostile Native Americans in the western country. Their final demarcation determined the Maryland‐Pennsylvania boundary at parallel 39°43′17.6∈ N. In 1769 the British crown ratified the line; in 1784 it was extended to settle the Pennsylvania and Virginia (now West Virginia) boundary. The novelist Thomas Pynchon offered a fictionalized account of the project in Mason and Dixon (1997).

In the Antebellum Era the Mason‐Dixon Line marked the division between the northern free‐soil and southern slave states. With the 1820 Missouri Compromise, Congress applied the term to a line extending from the Pennsylvania border, down the Ohio River to its Mississippi River outlet. Since the Ohio River flowed in a southwesterly direction, Congress established the line at 36°30′ west of the Mississippi. The Mason‐Dixon Line, thereby, divided the nation geographically over the slave issue. It later became embedded in popular usage as a convenient shorthand for demarcating the northern boundary of the South.
See also Colonial Era; Penn, William; Regionalism; Slavery: Development and Expansion of Slavery.

Bibliography

Judith St. George , Mason and Dixon's Line of Fire, 1991.

Nicholas Casner