Here is an excerpt from "Personal Property Tax Payers of Highland County, Ohio" by David McBride. Looks to me like there aren't any William Jacksons paying taxes in Penn prior to 1860. Not sure when Penn was created tho... I don't see it listed in censuses prior to 1860.

http://www.bishir.org/misc/JacksonPersonalTaxesHighlandCoOH....

I did a quick skim through the Jacksons in the Recorders Office records 1805-1850 and saw a lot of Gideon Jackson references but none with the names you listed. But they may have not owned any land before 1850 anyway. Also didn't see your people listed in the Cemetery Inscriptions book (but did find Gideon!)

No references to them in the Elsie Johnson Ayres books either.

Don