From Williamsport:

Take I-180 E  toward MONTOURSVILLE.  Take the PA-405 S exit, EXIT 13A, toward MUNCY.  Turn RIGHT onto PA-405 W. Turn LEFT onto S MAIN ST.  12 S MAIN ST is on the RIGHT.

Take I-180 W  toward WILLIAMSPORT.  Take EXIT 10 toward MAIN STREET.  Turn LEFT onto SUSQUEHANNA TRAIL RD.  SUSQUEHANNA TRAIL RD becomes S MAIN ST.  12 S MAIN ST is on the LEFT.