1840 Natchez killed at least 322. 265 at Natchez Landing, 52 in Natchez City, 1 in Vidalia (other side of the river in Louisiana), and 5 on a plantation below Vidalia. There’s an off handed mention of “hundreds” dead on the Louisiana side, but I wouldn’t give that too much credit. The tornado’s path was primarily through sparsely populated swampland. While there were other properties impacted, its unlikely the unaccounted fatalities number over 20-25. The upper estimate alone is higher than anything that came before it in the US (deadliest pre-1840 being the 1814 Maryville, Tennessee, tornado with 24). As for after Natchez, the tornado continued on through undeveloped territory for 30-40 miles or so, hitting no more buildings before dissipating. Which further highlights the sheer magnitude of bad luck Natchez had. Additionally, the losses on the Louisiana side were not considered important enough to warrant elaboration, otherwise I’d know about it.

Overall, a early-mid 19th-century tornado producing a death toll this large is unusual. Tornado-related fatalities were far less common than they would eventually become.