My initial response was to simply write it off as a crazy census taker. After all, I had attended quite a few genealogy lectures by that point in time and had also read several how-to books and knew that some census takers were not concerned about accuracy.
Of course I don't know who provided the information to the 1900 census taker for this enumeration. The place of birth for the long-deceased mother is most decidedly secondary information in this enumeration. The husband did probably not even know his of wife until the late 1850s when they met in Hancock County, Illinois. They married in 1868. He had no first hand knowledge of where she was born.
Obviously her children did not either.
The information is incorrect and some in genealogy circles would say "throw it out" as it's not good evidence.
But it is a clue.
Franciska's parents spent few short years elsewhere before they came to Illinois where their daughter was born in 1851.
That place: Ohio.
Those wrong places can be clues. Had I not learned of the Ohio connection another way--that would have been a place to look for the missing parents, based upon the census enumeration for Franciska's children twelve years after her death that gave a wrong place of birth.
Just because something is not evidence does not mean it is not a clue.