The Mason–Dixon line, also called Mason's and Dixon's line, originally determining the border between Maryland and Pennsylvania, was surveyed and marked between 1763 and 1767. Two English surveyors, Charles Mason and Jeremiah Dixon, were hired by the Penn and Calvert families to settle a border dispute. In 1760 the British crown, tired of the violence between the two colonies, demanded the dispute over the border between Maryland and Pennsylvania be settled according to an agreement made in 1732. The line the two surveyors came up with was so accurate it is still considered a marvel. GPS measurements show the line to be off by an inch or less in places and no more than in others.