Explosions at the J. A. Denn Powder Company, in Hawk's Prairie near Lacey, kill 10 and injure seven on June 27, 1934.

  • By Daryl C. McClary
  • Posted 7/08/2007
  • HistoryLink.org Essay 8155

On Wednesday afternoon, June 27, 1934, 10 people are killed and seven are injured when two explosions demolish the J. A. Denn Powder Company plant on Hawk’s Prairie, eight miles east of Olympia.  An 11th victim, the company chemist, will die from his injuries the following day.  Thurston County authorities investigate the accident, but so little of the plant remains that the official cause will remain a mystery.

Manufacturing Dynamite

The J. A. Denn Powder Company was located approximately two miles east of the town of Lacey and eight miles east of Olympia, the state capital. Built in 1933, the plant sat on 10 acres of grassland, surrounded by a buffer zone of second-growth Doug-fir trees, in a sparsely populated area known as Hawk’s Prairie.  The plant consisted of eight main structures: a powder mixing building and a powder magazine, both constructed of concrete, a cartridge packing building, a boiler room, two store rooms, and an office.  For safety, the entire compound was surrounded by a barbed-wire fence to keep out trespassers.  Several cottages had been built near the compound, providing housing for the plant managers and some of the workers;  however most employees commuted from nearby communities.  The plant ran two shifts, morning and evening, each with about 15 to 20 employees, depending on the workload.

The company, headquartered in Portland, Oregon, was owned by Joseph A. Denn, age 37.  Although not a chemist, Denn had worked as a salesman for a chemical company in Perth Amboy, New Jersey, which is where he got the idea to manufacture explosives.  Dynamite was in great demand in the Northwest, especially in rural areas where farmers used it for clearing stumps and other agricultural purposes.  It was also used extensively in mining, demolition, and construction.  The product was relatively cheap and easy to manufacture, but it was a dangerous business and lethal accidents were common.  The Lacey area, with a population of approximately 400, was also home to another explosives plant, the Giant Powder Company.

Basically, dynamite is made of nitroglycerin absorbed in a porous filler material, such as sawdust or diatomaceous earth to make it less shock-sensitive, and a small admixture of sodium carbonate, ammonium nitrate or cellulose nitrate.  Dynamite can also be made of a mixture of ammonium nitrate and nitrocellulose without nitroglycerin.  The mixture is packed into cardboard cartridges, usually about eight inches long and one inch in diameter. Then the ends are crimped and the sticks are sealed in a bath of hot paraffin.  A stick of dynamite is normally quite stable, requiring a blasting cap for detonation.  The greatest dangers were in the manufacturing process, where a spark could ignite flammable materials or trigger an explosion.

A Terrific Blast

On Wednesday afternoon, June 27, 1934, two explosions wracked J. A. Denn Powder Company plant. The concussions knocked the time-clock off the wall in the office, stopping the hands at 3:56 p.m.  The blasts demolished six of the eight buildings in the compound, including the concrete powder mixing building. The only buildings not destroyed were the powder magazine, a concrete building containing more than eight tons of dynamite, and the office.  The blast damaged the magazine’s roof and gables, but its store of explosives was unaffected.  The office, 150 yards from the blast and partially sheltered by the concrete magazine, also survived, but sustained substantial damage to one end of the building.

The first blast was thought to have occurred in the powder mixing building.  It leveled the concrete building, spread wreckage over a wide area and started several grass fires.  A second blast sent debris and a huge cloud of gray smoke several hundred feet into the sky.  Pieces of wood and scraps of metal were flung into trees hundreds of yards away.  Windows were shattered and furniture was toppled in the nearby company houses.  Inside the compound, flaming wreckage was scattered amid sticks of dynamite that lay everywhere among the bodies of the victims.  Raging grass fires hindered early rescue efforts, but they were brought under control by volunteer firefighters and the Civilian Conservation Corps who used picks, shovels and plows to make firebreaks.  Seven of the victims were killed instantly by the terrific blast and three died in ambulances on the way to Saint Peter Hospital in Olympia.

The explosions were heard as far away as Tacoma, 22 miles north of Olympia and at first, people thought the noise had emanated from the huge DuPont Explosives Company plant in Dupont.  Joseph A. Denn, the owner, was away from the plant with a salesman, C. J. Ramsey, and was somewhere in Stevens Pass when it happened.  Denn read about the disaster in the newspaper and stopped in Everett to telephone Olympia for more information.  Then the men rushed to Hawk’s Prairie to access the damage.

The Investigation

Smith Troy, the Thurston County coroner as well as a deputy county prosecutor, began an immediate investigation of the disaster.  He was assisted in the inquest by Claude Havens, Thurston County Sheriff; William A. Sullivan, Washington State Insurance Commissioner, acting as ex-officio state fire marshal; and E. Patrick Kelly, Washington State Director of Labor and Industries.

During an interview, Troy told reporters: “So little remains of the plant and surrounding buildings , about all we can hope to do is question survivors.  It will be difficult to determine the causes, but we may discover who, if anybody, was responsible for the blast” (The Seattle Times).

Most of the survivors thought the explosion started with a fire in the powder mixing building where an electric motor on a chemical grinder had overheated.  There had been a big fire in the powder mixing building three months earlier with no explosions, so workers expected that nothing untoward would happen.  The 800 pounds of powder-mixture contained no nitroglycerin and, although flammable, shouldn’t explode without a detonator.  So, with help from workers in the cartridge packing building, the men confidently formed a fire brigade to extinguish the blaze with hoses and fire extinguishers.

Day of Disaster

The initial outbreak of the fire spread flames over Roscoe Deeds, working nearby, igniting his clothes.  He leaped into a safety tank containing water, extinguishing the flames.  Other workers grabbed a hose line and began to play water onto the fire.  Deeds, severely burned, climbed from the water tank and ran from the building, spreading the alarm.

Hazel Epley was coming out of the cartridge packing building when she saw Deeds had been injured.  She helped him into a truck at the edge of the compound where Henry A. Denn Jr. was working.  Denn said he’d take Deeds to Saint Peter Hospital in Olympia and shouted to his 12-year-old stepson, Oliver Wilson, who was playing nearby, that there was a fire in the plant and to run for safety.  Curious, the boy headed toward the mixing building instead and was killed by the subsequent explosions.

Epley decided to return and help the men fighting the fire.  She was within 35 yards of the building when she met Margaret "Peggy”"Skinner coming from the mixing building.  They had paused for a moment to talk when the building exploded.  By some quirk of fate, Epley was killed, but Skinner wasn’t.  She was thrown backwards some 50 feet and knocked unconscious, but suffered only minor cuts and bruises, and a temporary loss of hearing.

Edward Parker and Charles Carpenter were using a hose to douse the flames, but when the smoke and heat became too intense, Parker left the building, telling Carpenter and the others to follow.  Parker made his way to fence surrounding the plant, and was climbing over the barbed-wire when the blast occurred.  The concussion hurled him 100 feet beyond the fence, knocking him unconscious.  Parker sustained a mild concussion and minor cuts and bruises.  Carpenter and seven other employees failed to evacuate in time and were killed in the subsequent explosions.  One of the victims was Henry J. Denn Sr., the plant-owner’s father.

One survivor, Scott Yarboro, thought the initial blast occurred when William Bartow, the plant’s chemist, threw an outside switch, shutting off all electricity to the powder mixing building.  He said an electrical spark flew from one of the motors, causing a dust explosion which then detonated one-and-a-half tons of dynamite powder drying in the “cooling room” inside the building.

Two men who survived, George Denn, the plant manager and owner’s brother, and Glenn Moyer, the shift supervisor, were outside the building in the compound when the explosions occurred, escaping with cuts, bruises and burns, but no life threatening injuries.

It was by chance that more employees were not killed in the disaster.  The plant’s day-shift went to work an hour early that day to finish loading a shipment of explosives for a Montana mine. O. R. Mitchell, a company truck driver, said they finished the job by 3:00 p.m. and were sent home.  Hearing the explosions, he returned to the plant to help.  While searching through the wreckage, he found the plant’s time-clock which had been knocked off the office wall by the blast, the hands having stopped at 3:56 p.m.

The final victim of the disaster was William E. Bartow, the plant superintendent and chemist, who died at Saint Peter Hospital in Olympia, early Thursday morning, June 28, 1934.  His injuries included two severe skull fractures, with loss of some brain tissue, severe burns and internal injuries.

Shortly after the disaster, E. Patrick Kelly, director of Washington State Department of Labor and Industries, announced that insurance rates would be raised for all workers engaged in manufacturing explosives.  Although the state is obligated to pay compensation to the dependents of insured workers killed or injured in industrial accidents, under the state compensation law, the burden of the expense is passed on to the industry through higher premiums.

The inquest attempted to piece together the chain of events that ended with disaster, but the results were inconclusive.  Nothing had been discovered to indicate sabotage had anything to do with the explosions, and officially the cause remained a mystery.  Damage to the plant was estimated at $75,000, but the plant was only insured for $50,000.  It was never rebuilt.

Casualty List


  • John Quincy Adams, age 43, cartridge packing plant
  • William E. Bartow, age 46, plant superintendent and chemist
  • Charles Carpenter, age 55, powder mixing plant
  • John Clausen, age 24, powder mixing plant
  • Henry J. Denn Sr., age 67, ,powder mixing plant
  • Hazel Eppley, age 37, cartridge packing plant
  • Andrew Haydeen, age 29, truck driver
  • Alvin A. Smith, age 23, cartridge packing plant
  • Clarence Elton Ulery, age 36, cartridge packing plant
  • Purl Abraham Ulery, age 41, cartridge packing plant
  • Oliver Wilson, age 12, stepson of Henry A. Denn Jr.
  • Roscoe Deeds, powder mixing plant, severe burns
  • George Denn, age 25, plant manager, lacerations
  • Glenn Moyer, shift supervisor, concussion and severe burns
  • Edward F. Parker, age 42, powder mixing plant, bruises
  • Margaret "Peggy" Skinner, age 25, cartridge packing plant, cuts and bruises
  • Scott Yarboro, age 21, cartridge packing  plant, head and face lacerations

Sources: Russell Bookout, “Sitting on Dynamite,” The Atlantic Monthly, June 1929, p. 724; “Another Blast Victim Dies of Injuries,” The Daily Olympian, June 29, 1934, p. 1; “Final Chapter Is Written in Tragedy,” Ibid., June 30, 1934, p. 6; “Big Factory Hurled 1,000 Feet in Air,” Seattle Post-Intelligencer, June 28, 1934, p. 1; Peggy Skinner, “Woman Survivor Describes Tragedy,” Ibid., June 28, 1934, p. 1; “Worker Blown Out of Plant,” Ibid., June 28, 1934, p. 2; “Denn Plant Explosion Heard in Tacoma,” Ibid., June 28, 1934, p. 1; “Outside Cause Hinted in Blast That Killed 10,” Ibid., June 29, 1934, p. 2; “ Devastation of Powder Plant Recalls War Scenes,” Ibid., June 29, 1934, p. 2; “Ten Killed, Six Hurt in Powder Mill Explosion,” The Seattle Times, June 28, 1934, p. 1; “Survivors of Blast Relate Graphic Stories of Terror,” Ibid., June 28, 1934, p. 3; “11th Victim of Powder Plant Is Dead,” Ibid., June 30, 1934, p. 4; “Rates Higher for Powder Workers,” Ibid., June 30, 1934, p. 4; “Ten Are Dead, Six Injured in Olympia Powder Blast,” The Seattle Star, June 28, 1934, p. 1; “Survivors Tell Stories of Death Dealing Blast,” Ibid., June 28, 1934; “Death Toll at Olympia Is 11,” Ibid., June 29, 1934, p. 4.

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