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Looking back at the 1878 Washburn A Mill explosion

In a matter of seconds, a series of thunderous explosions destroyed what had been the city’s largest industrial building, along with several adjacent mills.

In the spring of 1878, the original Washburn A Mill exploded in a fireball of flames, thrusting debris hundreds of feet into the air.
Courtesy of the Minnesota Historical Society

The twisted girders and jagged brick walls that form the back of Minneapolis’ Mill City Museum provide a vivid reminder of the site’s dramatic history.

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In February 1991, fire swept through what was then the Washburn Crosby Mill, reducing the mill to smoldering ruins. Today, those ruins have been incorporated in a modern, 21st century museum, making it a unique architectural creation.

The first disaster to befall the riverfront site occurred 135 years ago. In the spring of 1878, the original Washburn A Mill exploded in a fireball of flames, thrusting debris hundreds of feet into the air. In a matter of seconds, a series of thunderous explosions — heard 10 miles away in St. Paul —  destroyed what had been the city’s largest industrial building, along with several adjacent mills.

miller's row
Courtesy of the Minnesota Historical Society
Riverfront mills, left to right: Washburn A Mill, Crown Mill, Empire Mill,
Pillsbury B Mill, Excelsior Mill, paper mill, and Northwestern Mill.

The A Mill was only four years old at the time. It had been built in 1874 by Cadwallader Washburn, a Wisconsin businessman from LaCrosse. The massive seven-story building was powered with Mississippi River water, diverted through a canal that ran through its lower level. With 200 workers  at its riverfront site near St. Anthony Falls, Washburn’s mill was one of the city’s largest employers.

At 6 p.m. on May 2, the plant’s large day crew completed its shift. It was replaced by the 14 men who made up the night crew.

An hour later three massive explosions boomed out, reverberating in waves all over town. The 14 men in the a mill were killed.

Later that week, an unidentified local resident provided an eyewitness account of the cataclysmic event. He reported seeing “a stream of fire” pouring out of the A Mill’s basement windows.

“Then each floor above the basement became brilliantly illuminated, the light appearing simultaneously at the windows as the stories ignited one above the other,” he recalled. “Then the windows bust out, the walls cracked between the windows and fell, and the roof was projected into the air to great height, followed by a cloud of black smoke, through which brilliant flashes resembling lightening passing to and fro.”

Within minutes the fire had spread to the adjacent Diamond and Humboldt mills. They also exploded, killing four more workers.

The city’s fire department worked all night in an effort to contain the fire. But the intense heat blocked its rigs and hoses from getting close enough to the site to have much of an impact.

The next day, on May 3, the Minneapolis Tribune told its readers, “Minneapolis has met with a calamity, the suddenness and horror of which it is difficult for the mind to comprehend.”

Ruins of Washburn A Mill after explosion
Courtesy of the Minnesota Historical Society
Ruins of Washburn A Mill after explosion

The Tribune went on to report that “in a twinkling of an eye, by an explosion that shook the city like a rocking of an earthquake, the largest, the highest, and probably the heaviest stone structure in Minneapolis, the great Washburn mill, which has been the pride and boast of our flourishing city, was leveled to the ground.

“Soon the burning buildings sent their messengers of flame on the wings of the merciless north wind on to other fields of destruction. … Considering the boisterous winds prevailing, and the combustible material in its path … the wonder is that the whole lower portion of the city escaped the fate with which it was threatened.”

Almost immediately, rumors soon began to spread about the causes of the Minneapolis  disaster, which was rapidly gaining national attention. In St. Paul, residents thought an earthquake had occurred. Others said they heard that a railroad car loaded with nitroglycerine had exploded in the mill district. An Indiana milling executive speculated that the river water from the Mississippi had decomposed, producing inflammable gas that ignited in the mill. Even the usually reliable New York Times reported, erroneously, that the explosions were caused by gases generated by the milling process.

At the inquest into the deaths of the 18 workers, John A. Christian, the A Mill’s manager, put the rumors to rest when he explained that the disaster had been caused by rapidly burning flour dust.

washburn memorial
Courtesy of the Minnesota Historical Society
A monument in Lakewood Cemetery memorializes those
killed in the explosion

His explanation was later confirmed by two University of Minnesota professors, S.F. Peckham and Louis W. Peck, who reviewed a series of controlled experiments that caused flour dust to explode. Peckham and Peck concluded that two of the millstones, running dry, had rubbed against each other, causing a spark that ignited the dust.

As the furor over the explosions began to subside, the Tribune speculated about the impact of the disaster on the local milling industry, now that the large share of the city’s production facilities had been destroyed. The paper noted that Minneapolis had only recently surpassed St. Louis and Buffalo in milling production and was now the country’s leading flour producer. … 

“All of the proprietors of the mills are wealthy men,” the paper noted. “They are energetic, enterprising and will no doubt immediately rebuild. But the least time in which they could rebuild, refurnish and put into operation would be six to eight months.”

Cadwallader Washburn, who had rushed to town after he got word of the disaster, announced that he would rebuild, even as the embers from his destroyed plant were still glowing.

Washburn kept his word. By 1880, his new A Mill was up and running. It was safer and more technologically advanced than its predecessor, with an even greater production capacity. The milling magnate opened his new plant in time to take advantage of the economic boom that Minneapolis would experience during the last two decades of the 19th century and into the 20th century. During those years the city’s milling production would continue to increase, reaching a high point during the World War I era.

The A Mill continued in operation even as the local milling industry underwent a decline. But age eventually caught up with the riverfront landmark, and the mill was finally closed in 1965. It remained, abandoned, until the 1991 fire.

Today, visitors to the Mill City Museum who ride the Flour Tower elevator hear a thundering boom intended to evoke the 1878 explosion. A more somber reminder of the 19th century disaster is located four miles away in Lakewood Cemetery. There a monument, erected in 1885, honors the memory of the 18 men who were killed when the mills exploded. A plaque lists their names. Just below it, the monument’s engravings include a sheaf of wheat, a millstone and a broken gear.