Sue,
The land records that you found 1857-1860 ~ were they in Portage County or Waupaca County?

Did you or anyone else look for a probate record? Since land was owned there should be a probate record to be found in whichever county land was owned in at the time of his death.

Since only her signature is on the Jan 21, 1860 deed and she is clearly a widow on the 1860 census (taken 22 Jun 1860) my guess would be that the 01 Mar 1859 death date is possibly correct. The Mar 1861 date might be a date on one or more of the probate papers which would include possibly a will, bond, inventory, final administration.

Ann