One of the deadliest hurricanes in U.S. history hits Galveston, Texas, on September 8, 1900, killing more than 6,000 people. The storm caused so much destruction on the Texas coast that reliable estimates of the number of victims are difficult to make. Some believe that as many as 12,000 people perished, which would make it the most deadly day in American history.

READ MORE: How the Galveston Hurricane of 1900 Became the Deadliest U.S. Natural Disaster

Galveston Island lies just off the Texas coast. It is long and narrow, about 28 miles long by 2 miles wide, and is barely above sea level. The harbor on the bay side of Galveston was a prime port with numerous rail connections. As a major hub for trade, thousands of people settled on the island at the end of the 19th century.

It was a Friday afternoon when the residents of Galveston first got an indication that a storm was imminent. For a few days the storm had been bearing down on the Texas coast, coming across the Gulf of Mexico from the Florida Keys. At the time, there was no reliable warning system in place for hurricanes; it was not until 1908 that ships began radioing the mainland about approaching storms.

The storm hit Galveston on Saturday, September 8, with sustained winds of at least 115 miles per hour; the town’s wind gauge blew away so the wind speed may have been even higher. A Category 4 hurricane, the storm brought with it an enormous storm surge and, by 3 p.m., water had covered nearly the entire island. It came in waves that were 15 feet higher than the mean tide. At the Bolivar Point lighthouse, there was a report that salt water spray from the ocean reached a height of 115 feet. Buildings crumbled and fell from the force of the water and high winds ripped the roofs off of nearly every building in town. Many Galveston businesses and families had installed slate roofs after a serious 1885 fire and these roofs became flying weapons of destruction as the hurricane tossed them through the air.

The St. Mary’s Orphanage collapsed and killed all the inhabitants. At the Ursuline Convent, 1,000 people gathered seeking shelter, but when a 10-foot retaining wall fell, the entire front part of the convent collapsed. Ships in the harbor were tossed into each other and some were later found 30 miles away. Survivors reported seeing corpses floating all over and around the island. Thousands died in Galveston and at least another 2,000 on the mainland coast also perished. Precise numbers will never be known, in part because thousands of bodies were disposed of in the Gulf of Mexico without being counted or identified. When Clara Barton of the Red Cross came to Galveston soon after the disaster she said, “It would be difficult to exaggerate the awful scene here.”

Galveston began to rebuild almost immediately. On October 2, 1902, construction began on a massive protective sea wall. Two years later, the wall, 16 feet thick by 17 feet high and constructed of cement, stone and steel bars, was complete. By 1910, the population of Galveston had grown to 36,000. Thanks to the city’s preparations, when a comparable storm hit in 1915, only eight people died.