A woman by this name, b. 9 Mar 1831, d. 6 Jul 1899, married my great-great-greatgrandfather as well, Richard Grimes (or Graham) Cowan. We have tried for years to find information on the two surnames. I have information that sheds some light on it, but would love to know more. What I have been told (and I believe this source is very reliable, from the wife of one of Richard's direct descendants in 1970) is that the Cowan family Bible shows her name as Donegan, but that the Dickson Co, TN, marriage certificate shows just Chapman. So we are left with "why?" (I also have variant spelling Dunagan in the Washington Co, AR, census of 1880.) Are you descended from Richard Cowan (in which case we're cousins) or from another husband of Louisa (perhaps named Chapman), which would help explain the name question? We've also wondered if Chapman were her maiden name and she were raised by a Donegan family. It's exciting to find someone who is researching this very person who is my direct ancestor and about whom we've had this question for so many years. I look forward to hearing from you.