, ▁about ▁ ▁east ▁of ▁what ▁is ▁now ▁Pennsylvania ' s ▁south west ▁corner . ▁ ▁In ▁ 1 7 7 4 , ▁commission ers ▁from ▁Pennsylvania ▁and ▁Virginia ▁met ▁to ▁negoti ate ▁their ▁boundary , ▁which ▁at ▁the ▁time ▁involved ▁Pennsylvania ' s ▁southern ▁border ▁west ▁of ▁Maryland ▁and ▁its ▁entire ▁western ▁border . ▁Both ▁sides ▁agreed ▁that ▁Pennsylvania ' s ▁grant ▁made ▁its ▁western ▁border ▁a ▁trac ing ▁of ▁the ▁course ▁of ▁the ▁Del aware ▁River , ▁disp la ced ▁five ▁degrees ▁( appro xim ately ▁ 2 6 5 ▁miles ) ▁to ▁the ▁west . ▁And ▁both ▁sides ▁thought ▁this ▁would ▁place ▁Fort ▁Pitt ▁in ▁Virginia ▁territory ▁( in ▁fact ▁it ▁would ▁not ▁have ). ▁With ▁that ▁in ▁mind , ▁the ▁governor ▁of ▁Pennsylvania ▁argued ▁that , ▁despite ▁the ▁agreement ▁reached ▁with ▁Maryland , ▁Pennsylvania ' s ▁southern ▁border ▁west ▁of ▁Maryland ▁was ▁still ▁the ▁ 3 9 th ▁parallel , ▁about ▁ ▁south ▁of ▁the ▁Mason – D ixon ▁line . ▁Neg oti ations ▁continued ▁for ▁five ▁years , ▁with ▁a ▁series ▁of ▁proposed ▁lines . ▁In ▁the ▁end , ▁a ▁comprom ise ▁was ▁reached : ▁the ▁Mason – D ixon ▁line ▁would ▁be ▁extended ▁west ▁to ▁a ▁point ▁five ▁degrees ▁west ▁of ▁the ▁Del aware ▁River . ▁To ▁compens ate ▁Pennsylvania ▁for ▁the ▁claimed ▁territory ▁lost , ▁its ▁western ▁boundary ▁would ▁be ▁run ▁due ▁north ▁rather ▁than ▁copying ▁the ▁course ▁of ▁the ▁Del aware ▁River . ▁ ▁The ▁Mason – D ixon ▁line ▁was ▁marked ▁by ▁stones ▁every