1963 Indiana State Fairgrounds Coliseum gas explosion
On October 31, 1963, a gas explosion occurred at the Indiana State Fairgrounds Coliseum in Indianapolis, United States, killing 81 people and injuring about 400 others. It was one of the worst disasters in the history of the state.
Source: Wikipedia — 1963 Indiana State Fairgrounds Coliseum gas explosion (CC BY-SA 4.0)