I am on a similar hunt.Probably not related, but...
My grandfather (Charles Edward Kimble)was born in Hocking, OH in 1898.On his marriage certificate, His parents were listed as Amos Kimble and Rachel (Mae) Black.This was Amos' second marriage (assume the marriage part).Family folklore is that Amos, Rachel and son tried homesteading in Wisconsin, returning to OH around 1904.Amos died in 1906, leaving his son with another family (Literell?).Unknown what became of Rachel.
Your Rachel is the first I have found with a approximate birthdate that could work for mine.I saw a posting at one point which listed "Rachel Black" as a pioneer of Wisconsin and Montana.It could be she did not return from the homesteading venture.
Please let me know if you have since found further information for your Rachel.