The clocks in the Swift and Company building froze at 11:33 a.m., marking the moment a mighty explosion ripped through the structure. It was right before Christmas, December 14, 1949. The blast blew out parts of the west wall of the building and shattered all the windows. Floors and walls collapsed. The account in the Sioux City Journal declared, "Heavy steel doors and equipment throughout the structure were blown about like matchwood." The blast left a nightmare of twisted steel and tangled debris. Twenty-one people died and more than 90 people were injured.

On the day of the explosion, many workers were having lunch in another nearby building or the loss of life would have been even greater. Immediately, everyone ran to help. Despite overwhelming ammonia and gas fumes, workers began a frantic search through the wreckage, looking for their co-workers and friends.

The six-story building housed the main offices of Swift and Company along with other operations. Offices in the building received the full force of the blast. The room from which meat shipments were made was on the first floor. The third, fourth and fifth floors housed the sausage plant and smoke house. Offices, including those of the superintendent, were demolished. Hardest hit was the main floor and basement. The floor over the basement collapsed. Slaughtering houses located in the north end of the plant were not damaged as much.

Witnesses said that employees in the main office ran from the building with their clothes in tatters. Many of them were bleeding from wounds. Others suffered from ammonia burns.

Many told tales of narrow escapes and frightening experiences. One man explained that he was walking into the office from the loading dock when the blast tossed him into the air. He landed, somehow, underneath a platform scale. He could hear the chunks of concrete bouncing off the roof of the scale above him.

Another man was having a conversation with another worker when the blast occurred. He was lifted up and carried into the street on a piece of concrete, unharmed. The other man was knocked down and severely injured.

In a 1995 oral history interview with the Sioux City Public Museum, Jeanette Hansen recalled the explosion. She was working in the plant at the time, earning a little extra money for Christmas, and her husband worked in the dock area. After the explosion, she remembers "Somebody came and said 'get out of here. I've got a flashlight and follow me.'

"It was pitch black," she remembered. "I mean those walls are very definitely thick in the packing house".I said "I wonder where George is" my husband, and I saw somebody that I knew and I said "Have you seen George?"

" "Ya," he said. "I thought I saw him over across the street." Of course, he wasn't over across the street. He was down in the basement underneath a whole bunch of debris."

Hansen's husband was badly hurt in the explosion, required brain surgery, and spent time in a body cast. Remarkably, he recovered and went back to his job at Swifts. Mrs. Hansen was uninjured.

The Fire Department was first to arrive. Fortunately, there was little fire, and fireman quickly joined the volunteers in the search for survivors. Nearly all of the available firemen and policemen were called to the scene. All ambulances were called to duty, but there were not enough of them. Many of the injured were brought to hospitals in private vehicles. Governor Beardsley authorized the mobilization of the National Guard to help in the disaster. The Salvation Army and the Red Cross set up canteen stations to serve coffee and sandwiches to the victims and rescuers.

Ammonia and gas fumes spread through the area, creating fear of another explosion. The police used loudspeakers to warn rescuers and bystanders not to smoke. Some rescuers wore gas masks to prevent being overcome by the fumes. Swift and Company mechanics attacked the wreckage with hacksaws in the effort to clear the way for rescuers. They were afraid that the use of torches could spark another blast. Automobile wreckers and a huge airplane wrecker from the Air National Guard were brought in to help clear the heavy steel girders.

The bodies of the victims were taken to the Naval Reserve Armory at Fifth and Jones. Many had been killed by falling debris.

There were many heroic stories. One man, Art Stiles, was thrown to the ground outside the building. With smoke pouring through the doorway and concrete falling round him, he dashed into the building and carried three people from the wreckage. He later learned that only one had lived.

Natural gas was determined to be the cause of the explosion, but the blame was never officially assigned. Several years later, the Sioux City Journal reported: "It was never officially determined who was responsible for the explosion. However, payment of the $325,000 to Swift by insurance companies for the two gas firms indicate that they took the blame."