Dear Ms. Wade,
Thank you for posting your request on History Hub!
We suggest that you search the General Land Office Records from the Bureau of Land Management for land records of your ancestor in Duncan, Oklahoma. This site provides access to Federal land conveyance records for the Public Land States, including image access to more than five million Federal land title records issued between 1788 and the present. The database contains images of survey plats and field notes, land status records, and control document index records.
We hope this information helps with your research.
The National Archives and Records Administration