I found some evidence about her maiden name, and thus the surname of her father in a surprising place - the land records in the Jefferson County, Nebr., courthouse. Katharina was widowed twice, when her first husband and my great-great-grandfather Johann Barkmann died in 1879 and again when her second husband Martin Barkmann died in 1894. And each time while she was a widow, she conducted land transactions using the surname Bergmann. In contrast, she used her married surname of Barkmann each time she was involved in a land transaction while she was married, so this is evidence of her maiden name.
A few weeks after her first husband Johann died, she used the surname Bergmann when she bought eighty acres of land that adjoined their home place.
|Source: Warranty Deed, Peter & Anganetha Heidebrecht to Katharina Bergmann, 4 November 1879, Fairbury, Nebraska, Deed Book P:202, Register of Deeds, Courthouse, Fairbury.|
After she was widowed a second time, she sold seventy-seven acres of land to her son-in-law Klaas R. Friesen and used the surname Bergmann.
|Source: Warranty Deed, Katharina Bergmann to Klaas R. Friesen, 27 March 1899, Jefferson County, Nebraska, Deed Book 25:165, Register of Deeds, County Courthouse, Fairbury.|
This is another good piece of evidence that her father's surname was Bergmann and not Barkmann. When I analyzed her death certificate earlier, I felt that the evidence, while contradictory, was stronger that her father was Peter Peter Bergmann and not the Jacob Barkman listed on the death certificate. Now the evidence is even stronger for Peter Peter Bergmann being her father. And I certainly didn't expect to find it in the land records of Jefferson County, Nebr.
Collecting all the documents you can find and thinking about the implications of each one is crucial for doing good genealogy research.