Dear Vanette:
I asked my wife, who was brought up in Mont Alto and she said...
"All I know is Mont Alto is exactly 7 miles from Waynesboro-Could be somewhere between Waynesboro and Chambersburg - Who knows?" - Peg
Have you tried the Pennsylvania Room of the Alexander Hamilton Free Lbrary in Waynesboro. Ask to speak to the reference librarian.
Good luck, Jack