She was the world's oldest practicing pediatrician until her retirement in May 2001 at the age of 103, after 73 years.
She was a supercentenarian, living to the age of 114 years, 60 days.
On December 10, 2011, at age 113 years 312 days, she became one of the 100 oldest people ever.
(This record has since been surpassed.) At her death she was the 5th-oldest verified living person in the world and the 3rd-oldest verified living person in the United States.
A pioneering female doctor, medical researcher, and an outspoken voice in the pediatric community, Denmark was one of the few supercentenarians in history to gain prominence in life for reasons other than longevity.
She is credited as co-developer of the pertussis (whooping cough) vaccine.
She started treating children in 1928.
By the time of her retirement, Denmark was treating grandchildren and great-grandchildren of her first patients.