William McNown (no "I" I used the 'I' to differentiate William & Hugh who emigrated to Rawdon ca 1825 from brothers William II & Hugh II who emigrated to Indiana ca 1840) is your g-g-g-grandfather. He was born in Ardglass, Co. Down in 1868 & died Sept. 27, 1852 in Rawdon. Your William is the younger brother of my James who emigrated to Ormstown, Que in 1822.

You might want to visit a WEB site I (every now & then) maintain on the McNown's at:

http://home.attbi.com/~skmacn/index.html

I have designated the William line as the "B" line, my line is the "A" line. Under photos your g-g-grandfather John McNown (killed at Shiloh) is shown. John was born on the Isle-of-Man

I don't know how much you already knew but hope this helps.