Harold, on Pearl Edna Smitherman Ferguson. Since she died in 1970 and is on the Social Security Death Index, have you looked at her death certificate? With that late of a death date the person completing the information would surely have had knowledge as to who her parents were. That is one of the important things listed. She was born too early to have a birth certificate so you can't check there. Another thought is have you checked the newspapers when she died to see who was listed in her obit as next of kin other than just spouse and children? Even on the social security system they ask you for the names of your parents. She would have most likely been the one to complete her application for a social security number and would definately have known who her parents were. I have checked everything that I have and have access to and cannot seem to locate her. I even checked for census records in 1930, 1920 and 1910 with no luck even using wildcards in case the spelling of the name was listed differently.
Something else that you may not think about is that exact year of birth and census record year of birth is not always the same. I can certainly relate on that since my mother now asks me how old she is, and I am the youngest of her four children. I don't always remember and have to substract her year of birth in my head sometimes to even answer her. I just love the census records though, expecially when in one, a woman will list that she had 6 children and 5 are living and the next census she will lists that she had 5 children and all 5 are living. Makes me wonder.