The first World Down Syndrome Day (WDSD) was held on March 21st, 2006. The day and month of the day were not coincidental but were chosen specifically to correspond to 3 copies of the 21 chromosome.
Down Syndrome Association Singapore launched and hosted the WDSD website from 2006-2010, on behalf of DSi, for global activities to be recorded. On 19 December 2011, the United Nations General Assembly declared 21 March as World Down Syndrome Day.
Additionally, in 2023 a resolution passed in Arkansas naming March 21st World Down Syndrome Day.
Every year to observe WDSD, ADSA sponsors the lighting of Little Rock’s downtown bridges and the Two Rivers and Big Dam Bridges.