PA 416 was extended south from Mercersburg to the Maryland border southeast of Welsh Run in 1937 , following its present alignment .
By 1930 , the current alignment of the route between the Maryland border and PA 16 east of Mercersburg was an unnumbered , unpaved road .
PA   was extended south from Mercersburg to the Maryland border southeast of Welsh Run in 1937 , following PA 's present alignment .
By 1930 , the current alignment of the route between the Maryland border and PA 16 east of Mercersburg was an unnumbered , unpaved road .