1. In 1867, on December 6, the United States officially transferred the territory of Alaska from Russia in a ceremony held in Sitka. The event is now celebrated as Alaska Day.

2. On December 6, 1917, a catastrophic explosion caused by the accidental detonation of a ship carrying explosives killed more than 100 people in the city of Halifax, Nova Scotia. The disaster had repercussions in Alaska, which was then a U.S. territory, as Halifax was a major port of entry for food and supplies.

3. On December 6, 1957, the first successful test of a thermonuclear weapon took place on the Bikini Atoll in the Pacific Ocean. The blast had a yield of 2.5 megatons and was so powerful that it vaporized nearby islands.

4. In 1964, on December 6, a massive earthquake with a magnitude of 9.2 struck Alaska, causing widespread damage and numerous deaths. The quake remains one of the largest ever recorded in history.

5. On December 6, 1989, a lone gunman entered the École Polytechnique in Montreal, Quebec, and killed 14 women before committing suicide. The incident, which targeted female engineering students, sparked national debate about gun control and violence against women.