Here's a link to a grave in Sigourney which might be from your family:
http://www.findagrave.com/cgi-bin/fg.cgi?page=gr&GSln=hu...;
You might want to ask the woman who created the memorial if she's related to this family.

I've done a fair amount of research in Keokuk County (mostly Hedrick and Keota), and I've found that the Keokuk County Genealogical Historical Society and Museum can be helpful.
http://iagenweb.org/keokuk/resources/histsociety.htm

I would also look for any land which might have been sold after 1860. The KCGHSM can also help you with that.

Family Search is the official website for the LDS church's genealogy records. I've found things in there that I didn't find in Ancestry.
https://familysearch.org/

As a last resort, but possibly a really good one, you might hire a professional and see what they come up with. I did that quite a bit in the 1980's and came up with some very good results. I would assume that the ones you could hire in Ancestry would be good, but try to find one who's able to get access to the all of the records in Keokuk County. Again, KCGHSM might be able to help you find a researcher.

Good luck.

Kirk