The most infamous tornado in U.S. history occurred on March 18, 1925. The tornado, which started in Reynolds County, Missouri, became known as the "Tri-State Tornado" because of its massive effects on Missouri, Illinois and Indiana.
The Tri-State Tornado, which lasted for three hours, set U.S. records for distance and speed. It also set records for number of deaths and amount of destruction caused by a tornado. The 695 deaths attributed to this tornado are more than double those caused by the second-deadliest tornado, as of 2014. The Tri-State Tornado was part of a larger storm system in which several other major tornadoes appeared.