Koerwitz received her teaching certificate in 1924 from what was then the Oshkosh Normal School. She returned for her intermediate degree in 1944 and was offered a position at the University in 1947. Koerwitz was the first full-time librarian at the Rose Swart Campus School and also taught children’s literature courses, retiring in 1969 after 22 years. When she was 91, she wrote and illustrated a children’s book, Good Morning, Sun!
Koerwitz died in October 2002 at the age of 100. A generous bequest in her will funded purchase of books for the children's literature class. Her gift ensures that future students will understand and appreciate the power of the written word.