Wikipedia
558 - In Constantinople, the dome of the Hagia Sophia collapses.
1697 - Stockholm's royal castle is destroyed in a huge fire.
1840 - The Great Natchez Tornado strikes Natchez, Mississippi, killing 317 people. It is the second deadliest tornado in U.S. history.
1915 - World War I: a German U-boat sinks the RMS Lusitania, killing 1,198 people. Note: If I remember correctly, this was one of the main instigators for US involvement in the war.
1964 - A Pacific Air Lines Fairchild F-27 airliner crashes near San Ramon, California, killing all 44 aboard; the FBI later reports that a cockpit recorder tape indicates that the pilot and co-pilot had been shot by a suicidal passenger.
1992 - Three employees at a McDonald's Restaurant in Sydney, Nova Scotia, Canada, are brutally murdered and a fourth permanently disabled after a botched robbery. It is the first fast-food murder in Canada. Note: Why do you keep statistics like "First first-food murder in Canada"?
2002 - A China Southern Airlines MD-82 plunges into the Yellow Sea, killing 112 people.
So, on a more positive note, a couple of less deadly things that have happened:
1824 - World Premiere of Beethoven's Ninth Symphony.
1847 - American Medical Association is founded.
1945 - Germany signs surrender papers to end their involvement in WWII, effective May 8.
Alright, maybe I'll finish my paper now. :(