If you’ve ever had the chance to visit Liberty State Park in New York Harbor, you may have seen a plaque that reads: “You are walking on a site which saw one of the worst acts of terrorism in American history.” It’s not talking about 9/11.

As this piece from theobserver.com explains, Hudson County was the scene of a lethal act of sabotage that helped pull America out of its isolationist stance and get involved in the First World War.

From the story:

“At 2:08 a.m. on a sultry summer’s night, millions of pounds, thousands of tons, of ammunition stored on an island just off the Jersey City shoreline began exploding — and the earth began quaking (at an estimated 5.5 on the modern Richter scale). So massive were the chain-reaction blasts, there were reports of people being thrown from their beds. Windows in a 25-mile radius were shattered.”

“Throughout the metropolitan area, people rushed into the streets in terror. Shrapnel struck buildings throughout Jersey City, and the sky above the harbor was filled with ‘bombs bursting in air.’”

The site of the explosion was Black Tom Island, located just west of Liberty Island, on July 30 1916. This Saturday marks the centennial anniversary of the incident. The story says that, on the day of the explosion, there were somewhere between 2 million and 4 million pounds of explosives just sitting in freight cars, barges, and ships.

“There were all types,” says a 1964 edition of The American Legion Magazine. “From small arms ammunition to deadly TNT in bulk. No one ever knew exactly how much ammunition or the types of ammunition that were stored at Black Tom at any given moment.” One of the barges, “moored tight against the pier in blatant violation of safety laws” contained 100,000 pounds of TNT and 417 cases of detonating fuses.

At first, it was thought that the explosion had been caused by smudge pots some island guards had lit to ward off the swarms of mosquitoes that plagued the swampy area. The guards were even arrested, but later released when sabotage by German agents was deemed the more likely scenario.

The investigation went on for years until 1939, when the Lehigh Valley Railroad won the suit it had filed and Imperial Germany was judged responsible. However, the final payment of reparations totally $50 million wasn’t made until 1979.

The massive explosion certainly left its lasting marks. The exact death and injury tolls were never finalized. Injuries were estimated in the hundreds, but early reports of 50 dead were later reduced to just seven, likely because the explosions occurred in the middle of the night when workers and longshoremen were at home, the story says.

Reportedly, a 10-week-old infant was killed after being thrown from his crib by the blast.

Property damage was estimated at $20 million in 1916 dollars. That’s about $500 million today. Part of that property damage was the Statue of Liberty.

The statue’s torch was damaged by shrapnel from the explosions and immediate repairs were made. However, even after the 1984-86 centennial refurbishing of the statue, that part remains off-limits to the public. If you ever visit the statue, you’ll see that the staircase that goes up to the torch is blocked.

As for Black Tom Island itself, there wasn’t much left of it. Today, it’s a small piece of land joined to Liberty Island by landfill.

This Saturday, July 30, at 10 a.m., a ceremony to honor the Black Tom victims will take place at Liberty State Park. It will be held at the Flag Plaza, which is where the plaque citing the incident is located.

For the full story from The Observer, go here.