What was the deadliest single tornado in U.S. history?

The Tri-State Tornado was the deadliest single tornado in U.S. history. On March 18, 1925, it crossed parts of Missouri, Illinois, and Indiana, killing 695 people and injuring more than 2,000.

The tornado began in southeastern Missouri and moved through southern Illinois before dissipating in southwestern Indiana. It devastated communities including Murphysboro, Gorham, and De Soto. Murphysboro suffered the highest single-city death toll, while a school collapse in De Soto killed 33 students. Fires that broke out among the wreckage increased the suffering after the tornado passed.

The storm occurred before the Fujita Scale was created, so it received no official rating at the time. Based on the destruction, researchers generally consider it equivalent to an F5, the former top category. Historical accounts describe a path about 219 miles long and a duration of roughly three hours and 45 minutes.

Modern analysis questions whether every reported section belonged to one continuous tornado or to a family of tornadoes. That debate affects its path-length record, but not the established historical record of 695 deaths attributed to the Tri-State Tornado. It remains the deadliest tornado in American history.