MASON AND DIXON'S LINE. The boundary line between the States of Maryland and Pennsylvania, as run by two distinguished English surveyors, Charles Mason and Jeremiah Dixon, during the years 1763-67, and popularly accepted prior to the Civil War as the dividing line between the free States and the slave States. The line was the result of a dispute between the States of Maryland and Pennsylvania over their respective boundaries as described in their charters. The chief controversy turned upon the meaning of the phrases ‘the beginning of the 40°’ and ‘the beginning of the 43° of N. Lat.’ employed in the description of the Pennsylvania boundary. The quarrel, in which Lord Baltimore and Penn soon engaged, continued for more than eighty years; was the cause of endless trouble between individuals, and occupied the attention of the proprietors of both provinces, the Lords of Trade and Plantations, the High Court of Chancery, and the Privy Councils of three kings. No compromise was reached during the life of Penn, but, after his death, his sons succeeded in obtaining from Charles, Lord Baltimore, in 1732, an agreement by which the boundary line was to be drawn by commissioners representing both parties to the controversy. Baltimore at once came over with his commissioners, but was unable to get the Pennsylvania proprietors to take action. The unsettled condition of the boundary, therefore, continued and with it increasing disturbances in the disputed territory. The Governor of Maryland then laid the matter before the Proprietary and the King, and invoked their intervention for the settlement of the dispute. By an order in Council the King commanded both sides to keep the peace and instructed the Proprietaries to grant no lands in the disputed territory until the boundary could be adjusted. Pending a decision of the question by the English Court of Chancery, to which the matter was submitted in 1735, both parties agreed upon a provisional boundary. A decision was finally reached in 1750 by the Chancellor, Lord Hardwicke, which, with the agreement of 1732, served as the basis of a compromise between the proprietors in 1760. Commissioners representing both sides were appointed, and the eastern boundary was determined. To run the east and west line, as well as other parts unsettled, Mason and Dixon were appointed in 1763, and at once entered upon their task. By the year 1767 they had carried the line over the mountains to a point 244 miles from the Delaware River. Farther advance was stopped by the Indians, but the line was subsequently completed by others. The boundary was marked by mile-stones, every fifth one having the arms of Baltimore engraved on one side and those of Penn on the other. Its exact latitude is 39° 43' 26.3" North. A resurvey of the line was made in 1849, and in 1900 another resurvey was authorized by the States of Pennsylvania and Maryland, the work being placed under the direction of the commission consisting of the Superintendent of the United States Coast and Geodetic Survey, the Secretary of Internal Affairs of Pennsylvania, and the Director of the Geological Survey of Maryland. Consult: Browne, Maryland, the History of a Palatinate (Boston, 1884); Donaldson, The Public Domain (3d ed., Washington, 1884); and Hinsdale, The Old Northwest (Boston, 1899).