From which of Henrietta & Mathew Jared Cox's children do you descend? I descend from the same line (Benj. Biggs Sr. & Henrietta P.D.M. Munday) via William Biggs' (Mississippi's father) sister, Prudence Drusilla (Biggs) Ogle and have much info on this line, including a likeness of William from a newspaper, some of his old letters, old letters from Rev. James Lemen, Jr., talking about the family, etc.
Before moving to St. Clair Co., IL, William lived in what is now Monroe Co., IL. His cabin has been saved and is now located in Waterloo, IL. He was the first sheriff of St. Clair Co., IL (perhaps the first sheriff of the entire state as St. Clair was the first county.)
I have just proven Benj. Biggs, Sr.'s (Civil) service in the Rev. War to the NSDAR and descendants of his daughters are now eligible thru this line, if interested and they haven't already joined via their husbands' (Capt. James Moore & Capt. Joseph Ogle) lines and long-ago proven service
I assume you've seen the book William Biggs wrote about his captivity by the Kickapoos?