Her sister Bessie was the second black woman to be granted a dentistry license in New York state. While these two postions awarded the sisters freedom from persecution in the workplace, it wasn't until the early 1990s, when both were over 100 years old, that they gained fame.
In 1992, the two sisters published a book called Having Our Say: The Delany Sisters' First 100 Years, which dealt with the trials and tribulations the sisters had faced during their century of life. The book was highly successful on the best seller charts, and even spawned a Broadway play. They followed this up in 1994 with The Delany Sisters' Book of Everyday Wisdom.
After Bessie's death in 1995 at age 104, Sadie wrote another book called On My Own At 107: Reflections on Life Without Bessie, dealing with the loss of her sister. Sadie lived on until her death at the age of 109 in 1999.
The sisters were included in the Guinness Book of World Records in 1993 as the world's oldest authors.