The founder of Chabad Chassidism, Rabbi Schneur Zalman of Liadi (1745-1812), passed away on the eve of the 24th of Tevet, 5573, at approximately 10:30 pm, shortly after reciting the Havdalah prayer marking the end of the Shabbat. The Rebbe was in the village of Peyena, fleeing Napoleon's armies, which had swept through the Rebbe's hometown of Liadi three months earlier in their advance towards Moscow. He was in his 68th year at the time of his passing, and was succeeded by his son, Rabbi DovBer of Lubavitch.
Link: The Life and Teachings of Rabbi Schneur Zalman of Liadi
A devastating earthquake struck northern Israel, killing four thousand Jews in Safed and between 700 to 1000 Jews in Tiberias. Many of the survivors migrated to Hebron, rejuvenating the developing Chabad community established there 10 years earlier by the second Rebbe of Chabad, Rabbi DovBer of Lubavitch.
One of the first hospitals in America under Jewish direction, Mount Sinai Hospital, was founded in New York on this date in 1852.