You may already know all of this,
"The Descendants of John Plum from West Virginia" lists Mary Plum (b.1818 in Hamilton Township, Franklin County, Ohio)who married first James Fleming and later his brother, Robert Fleming. She was the granddaughter of John Plum and Rachel Temple,and the daughter of Jacob Plum and Mary Magdalena Stimmel. Mary Plum Fleming later moved to Iowa. She had two sons, James and Robert Fleming. No dates are given for their births or for the move.
However, two of her brothers, John and James Plum, moved to Tazwell Il before 1846. One of her sisters, Rachel Plum and her husband, Samuel Rohr left Ohio for Iowa and Wisconsin sometime after 1845. You can trace many of the Plum family through Ancestry.com
Suggestions: If you find no land records, look for business directories. The family apparently had many members who were wheelwrights and wagon/carriage makers as well as farmers.
The report I cited above is by L.P Fauskes and dated 1992. I believe copies are available through the LDT libraries.