In 1866, John Langdon Down, a British doctor, described what is now known as “Down syndrome” named after himself. The syndrome was first described, as “Mongolism” and the term Down syndrome didn’t become the accepted term until the early 1970s.

More was learned about the condition in 1959 when French Pediatrician/Geneticist Professor Jerome Lejeune discovered that individuals with Down syndrome have an extra chromosome—just one year before the National Association for Down Syndrome (NDS) was founded. Shortly thereafter, chromosome studies were developed to confirm the diagnosis of Down syndrome.