In 1763, a century of sometimes violent conflict between the Calverts and Penns had ended and the boundaries between their Pennsylvania and Maryland proprietaries were fixed. To ensure that Philadelphia remained in Pennsylvania, the boundary was set 15 miles south of the southernmost house in Philadelphia. Astronomers Charles Mason and Jeremiah Dixon were hired by the sons of William Penn and and the degenerate Lord Baltmore, Frederick Calvert, to mark the boundaries.
