▁at ▁Union ▁M ills , ▁followed ▁by ▁nearly ▁two ▁weeks ▁at ▁Be ale ton . ▁It ▁returned ▁to ▁Union ▁M ills ▁until ▁mid - J une , ▁then ▁for ▁ten ▁days ▁elements ▁of ▁the ▁regiment ▁were ▁stations ▁at ▁Br isto e ▁Station , ▁Cat lett ' s ▁Station ▁and ▁Man ass as . ▁▁ ▁On ▁June ▁ 2 5 , ▁the ▁brig ade ▁was ▁assigned ▁as ▁the ▁ 3 rd ▁Brigade , ▁ 3 rd ▁Division , ▁I ▁Corps , ▁and ▁ordered ▁to ▁form ▁the ▁rear ▁guard ▁of ▁the ▁Army ▁of ▁the ▁Pot om ac ▁as ▁it ▁march ed ▁north ▁after ▁Robert ▁E . ▁Lee ' s ▁Army ▁of ▁Northern ▁Virginia . ▁The ▁ 1 5 th ▁march ed ▁with ▁the ▁brig ade ▁from ▁Wolf ▁Run ▁Sho als ▁on ▁June ▁ 2 5 , ▁crossed ▁the ▁Pot om ac ▁River ▁on ▁June ▁ 2 7 , ▁at ▁Edward ' s ▁Fer ry , ▁and ▁moved ▁north ▁through ▁Frederick ▁and ▁Cre ager st own , ▁Maryland . ▁It ▁was ▁drawing ▁near ▁G ett ys burg ▁on ▁July ▁ 1 , ▁when ▁the ▁ 1 2 th ▁and ▁ 1 5 th ▁reg iments ▁were ▁det ached ▁to ▁guard ▁the ▁corps ▁trains . ▁The ▁two ▁reg iments ▁accompanied ▁the ▁corps ▁trains ▁to ▁Rock ▁Creek ▁Church , ▁near ▁the ▁battle field . ▁ ▁After ▁the ▁battle , ▁regiment ▁participated ▁in ▁the ▁purs uit ▁of ▁Lee ' s ▁Army ▁of ▁Northern ▁Virginia ▁across ▁the ▁C ato ct in ▁mountains ▁to ▁M idd let own , ▁Maryland ,