Home World September 11: When was 9/11? How many died?World September 11: When was 9/11? How many died? Byfloridapost -September 10, 2020 0 Facebook Twitter Pinterest WhatsApp SEPTEMBER 11 marks a day of national mourning in the US, as people across the country remember one of the most shocking attacks on American soil. When was 9/11, and how many people died?