Hello Tistra,
I didn't have any help for you in my computer files, but I checked census records in Iroquois County IL and thought the 1860 census was somewhat helpful. First, both 1860 and 1870 Census records for Isaac say that he was born in New York state, which provides a bit of consistency but is different from what you have. The 1860 census (Roll 186, p. 124) lists places of birth for Isaac and his family. You can track his migration with that 1860 census record: Isaac b. NY, Eliza (Miller) b. PA, James b. 1845 OH, Loretta and Mary R., ages 10 and 6, born NY. In 1870 (Roll 231, p. 438), Isaac is not listed in the index but his wife Eliza is. The two of them and their now-16 year old daughter Mary are living with another family who is headed by David Northop, also born NY. The Northop family might lead you to more information about Isaac; at least, it is worth a try.
~ Melanie