Overturned trains. Timber found miles away from where it had been stored. Trees felled. Fires and close calls. A letter that flew almost 100 miles. On a normal day in the Midwest in 1925, any one of these stories would have been worthy of front-page coverage. But March 18, 1925, was a day like no other the region had ever seen.

That day, a huge outbreak of tornadoes marched across a swath of the Midwest and Southeast. The largest of them all—the deadliest tornado in United States history—laid waste to parts of Missouri, Illinois and Indiana. Now known as the Tri-State Tornado, it turned March 18 into a day of gruesome destruction and bizarre survival stories. 

Modern meteorologists believe wind speeds topped 300 miles per hour in some locations. At one point, observers in Missouri calculated that it was a full mile wide. 

It was a rare incident of the most dangerous and destructive type of tornado, and packed newspapers throughout the nation with tales of how nature’s terrifying wrath had uprooted life in sleepy towns with names like Biehle, Murphysboro, and Poseyville—in a time when meteorologists were forbidden from forecasting tornados or even using the word “tornado.”

The ban on the word had been in effect since the 1880s, when weather forecasters first began developing methods of predicting tornadoes. At the time, forecasting was in its infancy, and officials worried that meteorologists could not provide adequate forecasts of how a tornado might behave. They also underestimated the public, writes weather historian Marlene Bradford, and felt that telephone operators might panic if they were required to relay news of upcoming storms. “Meteorologists appeared to have reached a consensus that forecasting tornadoes would do more harm than good,” Bradford writes, and the Weather Bureau had an outright ban on the word until 1950.

Nonetheless, such storms were common in the Midwest and on the Great Plains, where thunderstorms and temperature instability feed tornadoes. But though people in Missouri, Illinois and Indiana were used to storms and tornadoes, they had never seen anything like the storm that developed the afternoon of March 18, 1925. 

A small tornado that touched down near Ellington, Missouri gained momentum over the course of the afternoon. In the three-and-a-half hours that followed, it ballooned to record widths and speed. At one point, observers calculated that it was a full mile wide, and it maintained an average speed of 62 miles per hour and a top speed of 73 miles per hour.

In 2013, a group of weather experts reevaluated the tornado in search of reasons why it was so huge and so destructive. Though they did find an unusual combination of a warm front, the tornado’s supercell and a favorable storm environment, they concluded that there wasn’t a single reason why the storm was so huge.

For people on the ground, the reasons didn’t matter. This tornado was the biggest one they’d ever seen, and people scrambled for shelter as it attacked town after town. From the start, the storm was a killer. Within minutes of materializing, it killed a farmer. Then it headed to Annapolis, Missouri, a mining town. Tragically, the mountains in the town kept people from spotting it. Ninety percent of the town’s buildings were destroyed, four people were killed, and 1,000 people became homeless. Miraculously, a group of children who had huddled around their teacher’s desk after coming in from recess survived.

That was just the beginning. Soon the tornado had marched through Murphysboro, Illinois, where 243 people were killed, 623 injured and the city’s industries decimated. In nearby De Soto, 7-year-old Betty Moroni was in her classroom when the storm hit. Thirty-three students died at the school, including Moroni’s sister and 19 of the children in the classroom where she cowered during the storm. She lost three sisters and her father eventually died of head injuries he sustained during the tornado.

“After the tornado was over, nobody knew where anybody was,” she told The Southern Illinoisian in 2015. “You could be blown forever.” The tornado killed 33 schoolchildren, and 36 others, in De Soto. The death toll was even higher in West Frankfort, and only three buildings were left standing in nearby Parrish.

Then the tornado jumped state lines again. This time, its target was Indiana. Owensville was first. “The body of an unidentified infant was found in a creek, where it had been hurled by the fury,” wrote a local reporter. After laying waste to much of Princeton, the storm finally petered out.

The day after the tornado, people were still picking through the wreckage. Hospitals were overflowing, and nearby cities sent contributions and rescue resources to help with fires and try to recover bodies. Overall, 695 people were killed in the tornado, still considered the most deadly on record. Modern meteorologists believe it was an EF5 on the Enhanced Fujita Scale. They believe that wind speeds topped 300 miles per hour in some locations.

Though the word “tornado” was still taboo among weather forecasters until 1950, the tornado did have one good effect. “The single biggest thing that happened as a result of the Tri-State was the increase in public awareness about tornadoes,” Harold Brooks, a NOAA severe storms expert, told Scientific American in 2007. “Even though the National Severe Storms Laboratory had a ban on using the word 'tornado,' it was the beginning of local tornado-spotter networks.”

Today, those spotters—and a weather prediction network that is unafraid of the word tornado—have contributed to a massive decline in tornado deaths. Massive tornadoes still strike the Midwest, but forecasters and residents hope they’ll never see the likes of the 1925 tornado again.