Sixty-nine years ago during World War Two the United States dropped the first atomic bomb on Hiroshima. Three days later the U.S. dropped another bomb on Nagasaki.
While Japan surrendered after the attacks more than a hundred thousand people died.
It was the first time nuclear weapons were used and people at the memorial Wednesday night hope it was also the last.
Cathy McGuire of the Ad Hoc Committee says, "The world's security would all be better off if every country who already has nuclear weapons got rid of them and that no more be proliferated."
This remembrance started back in the 80's after the Wabash Valley Coalition for Peace and Justice placed a memorial in the park.