Mason and Dixon
and the Defining of America

Iconic Treasures from the Maryland Historical Society, Independence Hall, and the Maryland State Archives

December 4, 2008 – February 28, 2009

Boundary Stone

Every American has heard of the Mason Dixon Line but few know exactly why the Line was created and just what it represents.

The name comes from two British experts: astronomer Charles Mason and surveyor Jeremiah Dixon, who were brought in to settle a dispute that had raged for over 80 years between the Calverts of Maryland and the Penns of Pennsylvania. The Calverts and the Penns couldn’t agree where the true boundary between the two colonies lay. Beginning in 1763, Mason and Dixon spent five arduous years surveying the boundary line for 312 miles. They began on the Eastern Shore in what is now Delaware, then followed a constant latitude west from a point 15 miles south of Philadelphia. Their survey ended in 1768 at the “Great Warrior Trail” in the territory of the Six Nations.

The current exhibition focuses on the extraordinary scientific and engineering achievement represented by the world’s first major geodetic survey.

Among the artifacts and documents on view are:

  • The Transit and Equal Altitude Instrument used by Mason and Dixon. Made especially for them by London’s master instrument maker John Bird, this was the finest geodetic instrument of its age. It enabled Mason and Dixon to determine true north by tracking stars where they crossed the meridian.
  • the1763 parchment of the Articles of Agreement between Thomas and Richard Penn of Pennsylvania, Frederick, Lord Baltimore, of Maryland, and Charles Mason and Jeremiah Dixon for surveying the boundary, complete with signatures and wax seals for all parties.
  • Mason and Dixon’s hand-written journal
  • the original 1768 map, printed by Robert Kennedy of Philadelphia from Mason and Dixon’s hand drawn copy. The Boundary Commissioners for both colonies signed this print of Mason and Dixon’s “true and exact” plan and affixed their wax seals. After completing their monumental task, Mason and Dixon returned to England. Jeremiah Dixon died there in 1779. Charles Mason came back to America with his wife and eight children in 1786, but died shortly after and is buried in an unmarked grave in Philadelphia. No portraits exist of the two men who played a key role in the defining of America, but their Line lived on.

Under the terms of the Missouri Compromise, enacted by the US Congress in 1820, the Mason-Dixon Line gained iconic status as the boundary between North and South, between free and slave-owning states. It also gave rise to the designation of the South as “Dixieland.”

A final note:

The Transit and Equal Altitude Instrument that Mason and Dixon used in their survey ended up in a small observatory behind Independence Hall in Philadelphia. It was on the steps of this observatory that the Declaration of Independence was first read to an assembled throng on July 8, 1776. During the Revolutionary War, the instrument disappeared and was re-discovered in 1912 hidden under the floorboards of the observatory’s bell tower.

For more information, here is the full article by David S. Thaler.

MdHS