Source : Webster's Revised Unabridged Dictionary (1913)

Whereon \Where*on"\, adv.
   1. On which; -- used relatively; as, the earth whereon we
      live.

            O fair foundation laid whereon to build. --Milton.

   2. On what; -- used interrogatively; as, whereon do we stand?

Source : WordNet®

whereon
     adv : on which; "land whereon to grow corn"