Possible Daughter of Helen and Allan - this one matches the birth date of Harriet Foster.
Harriet L. Evertsen
Born 24 July 1914 and died 19 March 1990
Last Residence: 62002 Alton, Madison, Illinois,
SSN was issued in Illinois (Before 1951)
Information on the other son sent by pm
Sandra
Added :- The obituary on the husband of the above Harriet does not lead me to believe it is your Harriet, even though the birth date is correct. Need to look a little more.
These seem to be the choices with the correct birth date 24 July 1914.

None seem to be suitable

No further forward on Harriet I'm afraid.

Harriet L. Evertsen 24 Jul 1914 19 Mar 1990 Alton, Madison, Illinois
Husband Edward R Evertsen born 1912 Died 23 rd June 1997 (obituary gives wife as Harriet Fichtel)
Harriet M. Gibson 24 Jul 1914 7 Sep 1996 Laurinburg, Scotland, North Carolina
Seems to be Harriet McNeil Gibson. Wrong race.
Harriet Agnes Leifeld 24 Jul 1914 19 Sep 2010 Hastings, Dakota, Minnesota
Maiden Name could be Lovejoy

Harriet I. Meister 24 Jul 1914 4 Sep 1995 Garvin, Lyon, Minnesota
Harriet O. Warstler 24 Jul 1914 28 Jul 2004 Pataskala, Licking, Ohio
Born Ohio - Maiden name looks like Steinmetz