As we mark the 20th anniversary of the attacks on the World Trade Center and Washington, D.C. that occurred on September 11, 2001, we reflect on the pain and loss of the events that shook the entire world, some of us very personally. Here, we also pause to note the progress and missteps that this day brought forth in disaster victim identification (DVI) efforts. At the time of the attacks, DVI protocols were still minimal and the U.S. federal database for crime and missing persons (the Combined DNA Index System, CODIS) was only three years old. Within hours of the attack, the Office of Chief Medical Examiner in New York City led a strategy to establish victim family centers. The ad hoc practices that emerged in those first days and months became both patterns for success and cautionary lessons. DVI challenges include how to share data, protect privacy, and obtain consent, in addition to how to communicate unexpected family relationships and employ trauma-informed practices for family reference sample management. In the last 20 years, DNA-based technologies have evolved to allow, for instance, testing of minuscule DNA fragments and analysis of samples within hours via rapid DNA instruments. These advances allow more and faster identifications in mass fatality events, but also bring new ELSI questions on when to apply technologies, how to prioritize and fund efforts, and how to manage data among stakeholders and families. One lesson we took from that day 20 years ago is preparedness – that both emotional and practical preparation can minimize challenges in the aftermath of a mass fatality. In remembering the victims of 9/11, both dead and alive, we look back on the scientific contributions resulting from this mass fatality and the ongoing ethical, legal, and social implications of using forensic data in humanitarian efforts.