You could check cemetery indexes for Rebecca Martin. Some can be found here: http://www.rootsweb.ancestry.com/~wirock/
And check FindAGrave. There are also printed indexes for some area cemeteries that are available at local libraries. (See: http://www.rootsweb.ancestry.com/~wircgs/RCGS_PUB.html
) If you're not in the area (as I'm not), you could try to find a volunteer to check them out for you.
1850 census - At the top of each page it should say "Free Inhabitants in _____________". There it will list the town, village or city enumerated on that page. You may want to check to see if they were enumerated in towns that are on the county line. You can find a couple of old plat maps of Rock County here: http://www.rootsweb.ancestry.com/~wircgs/
An old plat map of Dane County showing towns is here: http://www.danecountyhistory.org/1873plat/1873plat.html
Contemporary maps showing town boundaries are here: http://www.dot.wisconsin.gov/travel/maps/county.htm
Property records - Researching property records is a two-step process. First you need to look at the Grantor and Grantee indexes. These list all the property transactions by the Grantor's (seller's) or Grantee's (buyer's) names. These indexes are compiled in alphabetical sections - All the names beginning with A are in one section, those with B in the next, etc., but within each section the names are not alphabetized. Each entry will list the date, property description, and the volume in which the actual transaction is recorded. With that info, you can then get the microfilm for the volume(s) listed. If you aren't familiar with the township platting system, you might want to look into that before you start researching the property records. Here's a good start: http://www.lhaasdav.com/land/publicdomain.html