Check the WWI registration records. I found a Richard Curtis Campbell in Scurry, Texas. If she is with one of her sons she may be listed on the registration card.

You can check tax records and death certificates via the county where she would have been or sometimes with the state. Tax records are also good. Her sons and daughters death certificates may also say where the mother and father were born and died. I never checked a death certificate from Texas and therefore I don't know if they listed that info or not.