I live in Flat River, MO in St. Francois Co, MO.
I've hit a roadblock on my search and you may be the missing piece.

My mother is Linda McClanahan (Bismarck, MO).
Her father and mother is Bert L. and Betty McClanahan of Bismarck, MO.
My grandfather Bert L. had a bunch of brothers and sisters I only know some of their names.
His parents were David and Maudie C. McClanahan (Jackson st., Flat River, St. Francois Co, MO)
David's parents were Julia F. and William H. McClanahan.

William's parents' names aren't listed anywhere but it just says Illinois for his parent's place of birth.

I don't know. Just throwing it out there.