On January 23, 1556, an earthquake in Shaanxi, China, kills an estimated 830,000 people. Counting casualties is often imprecise after large-scale disasters, especially prior to the 20th century, but this disaster is still considered the deadliest of all time.

The quake struck in late evening, with aftershocks continuing through the following morning. Later scientific investigation revealed that the magnitude of the quake was approximately 8.0 to 8.3, which isn’t close to the strongest tremor on record. However, the quake struck in the middle of a densely populated area with poorly constructed buildings and homes, resulting in a horrific death toll.

The epicenter of the earthquake was in the Wei River Valley in the Shaanxi Province, near the cities of Huaxian, Weinan and Huayin. In Huaxian, every single building and home collapsed, killing more than half the residents of the city, a number estimated in the tens of thousands. It was a similar story in Weinan and Huayin. In some places, 60-foot-deep crevices opened in the earth. Serious destruction and death occurred as much as 300 miles away from the epicenter. The earthquake also triggered landslides, which contributed to the massive death toll.

Even if the number of deaths caused by the Shaanxi earthquake has been overestimated slightly, it would still rank as the worst disaster in history by a considerable margin.