One year ago today, one of the worst tornado outbreaks in recent history struck the heart of tornado alley. Specifically, Oklahoma, Kansas, and northern Texas experienced 76 tornadoes in less than 12 hours.

More than 40 people died in Oklahoma and Kansas, with nearly 800 injured. The total damage estimate in Oklahoma alone was 1.2 billion dollars, with approximately 10,000 homes and businesses damaged or destroyed.

In Oklahoma, one tornado reached F5 status, the highest level on the Fujita scale which ranks tornado damage. This tornado was the first F5 on record to invade the borders of Oklahoma City. Meteorologists chasing this twister measured a wind speed of more than 300 mph, setting a new world-record.