Barbara:

A few facts you posted caught my eye; one is the location in section 7 of Shields Township, the year that your ancestors bought their property (1840) and their country of origin (Ireland).

Among my ancestors were Thomas and Catherine (Loftus) Graham. They were Irish immigrants who bought land in 1840 in section 36 of Warren Township (where the former Lakehurst shopping center was later located). (If I'm not mistaken thats pretty close to section 7 of Shields Township)
Family lore is that my ancestors earned the money for their land by working on the Erie Canal in NY State prior to moving to Illinois. I don't know if this helps, but its possible that your ancestors may have spent some time in upstate NY before moving to Illinois.

Regards,
-Dave Adams-