ular ▁line ▁mid point ▁and ▁the ▁ 1 2 - mile ▁circle , ▁determine ▁the ▁tang ent ▁point ▁along ▁the ▁circle , ▁and ▁then ▁actually ▁survey ▁and ▁monument ▁the ▁border . ▁They ▁then ▁survey ed ▁the ▁north ▁and ▁arc ▁lines . ▁They ▁did ▁this ▁work ▁between ▁ 1 7 6 3 ▁and ▁ 1 7 6 7 . ▁This ▁actually ▁left ▁a ▁small ▁w edge ▁of ▁land ▁in ▁dispute ▁between ▁Del aware ▁and ▁Pennsylvania ▁until ▁ 1 9 2 1 . ▁ ▁In ▁April ▁ 1 7 6 5 , ▁Mason ▁and ▁D ixon ▁began ▁their ▁survey ▁of ▁the ▁more ▁famous ▁Maryland – P en nsylvan ia ▁line . ▁They ▁were ▁commission ed ▁to ▁run ▁it ▁for ▁a ▁distance ▁of ▁five ▁degrees ▁of ▁longitude ▁west ▁from ▁the ▁Del aware ▁River , ▁fixing ▁the ▁western ▁boundary ▁of ▁Pennsylvania ▁( see ▁the ▁entry ▁for ▁Y oh og ania ▁County ). ▁However , ▁in ▁October ▁ 1 7 6 7 , ▁at ▁D unk ard ▁Creek ▁near ▁Mount ▁Morris , ▁Pennsylvania , ▁nearly ▁ ▁west ▁of ▁the ▁Del aware , ▁their ▁I ro qu ois ▁gu ides ▁refused ▁to ▁go ▁any ▁further , ▁having ▁reached ▁the ▁border ▁of ▁their ▁lands ▁with ▁the ▁L ena pe , ▁with ▁whom ▁they ▁were ▁engaged ▁in ▁host ilities . ▁As ▁such ▁the ▁group ▁was ▁forced ▁to ▁quit , ▁and ▁on ▁October ▁ 1 1 , ▁they ▁made ▁their ▁final ▁observations , ▁ ▁from ▁their ▁starting ▁point . ▁ ▁In ▁ 1 7 8 4 , ▁survey ors ▁David ▁R itten