The 1917 May–June tornado outbreak sequence was an eight-day tornado event, known as a tornado outbreak sequence, that killed at least 383 people, mostly in the Midwestern and parts of the Southeastern United States. It was the most intense and the longest continuous tornado outbreak sequence on record, with at least 73 tornadoes including 15 that were analyzed to have been violent (F4–F5) based upon reported damage. The deadliest tornado of the entire sequence produced a 155-mile (249 km) track across Illinois, killing 101 people and devastating the towns of Charleston and Mattoon along with small farming communities.