Star observations were used to measure the Mason-Dixon Line
Mason and Dixon would spend weeks at a time measuring just one point of latitude by the stars, said Todd Babcock of the Mason and Dixon Preservation Partnership.
Days of calculations would follow before the pair and their survey team could move on.
But Mr Babcock added that the Mason-Dixon Line was not as accurate as first thought.
You can see more on this story on Inside Out on BBC One in the North East and Cumbria on Monday at 19:30 BST
30 Aug 2017