Thanks for the great map! I couldn't seem to find Thomastown on any other maps.
My ancestor was Thomas Farrell who married a Honora Lyons in Thomastown abt. 1810. They immigrated to the Quebec, Canada area abt. 1824.
Two of Thomas's grandsons (William & Timothy) ended up in Cheyenne, Wyoming with the railroad.
One of Thomas's great-great grandsons (my grandfather) added the O' back on in the 1930's.
Doesn't sound like a match to your John Farrell, but will keep my eyes open for any links.