To be honest, I never thought too much about Aunt Margaret in the 1940 census (shown here as a 28-year old living with her parents Mimka and Tjode Habben in Prairie Township, Hancock County, Illinois). The enumeration lists her as absent ("ab") and shows the two youngest children still living at home, which I expected. Aunt Margaret's occupation is listed as a teacher.
If the occupation is correct and she was working, the question is where.
I think Google Books may have given me the answer. A search on http://books.google.com for "margaret habben" (without the quotes) resulted in several hits, including two (the last ones in the image below) which seem to indicate that a Margaret Habben was teaching in Pike County, Illinois. The images of the books are not online and it may take a little doing to locate a copy, but the snippets do provide clues:
- the first match indicates a Margaret Habben was teaching Home Economics somewhere in Illinois
- the second match indicates (apparently) that she is teaching in Griggsville.