Oops! I forgot something in that last post! I noticed you live in Grayson County, TX. I've found where Rachel Foster Duggins is buried in Macomb Cemetery in Grayson County, TX. And Elijah is also buried there in an unmarked grave in Friendship Cemetery.
Rachel's date of death is February 3, 1825. I wonder if they had obituaries in the local newspaper then that listed the children, etc., like they had later in the 20th century. Do you know if there is a newspaper in Grayson County, TX that has been in business that long? Or if the local library would have it on microfilm?