Answer: The Tri-State Tornado of March 18, 1925 killed 695 people in Missouri (11), Illinois (613), and Indiana (71). The outbreak it occurred with was also the deadliest known tornado outbreak, with a combined death toll of 747 across the Mississippi River Valley.
killed 695 people and injured 2,027 others in Southern Missouri, Illinois and Indiana in 1925. The tornado went on for 219 miles, making it the longest ever recorded.
