I recall reading a magazine on local New Jersey history. I believe it was around Egg Harbor, maybe even further south, there was a large ammunition factory from WWI in NJ. It's all gone now, but at the time it was a BIG complex. The time frame is off but I wonder if there's any connection.
I live in Egg Harbor Township. A few months ago my neighbor had a load of topsoil delivered to his yard. He was spreading it with a Bobcat and uncovered a morter shell. He didn't know what it was, so he got out of the Bobcat, picked it up and leaned it against a tree. After awhile he decided to call the cops. 30 minutes later the whole neighborhood was shutdown. The punchline of the story is, he bought the topsoil from the neighbor on the other side of his house, who owns a development company. I don't think they've spoken to each other since.
One of the plants at teh company I work for was built on the site of a WWI munitions plant. Lots of stories of finding unexploded munitions during recent construction projects. Apparently there was an explosion there many decades ago. Every once in a while a shell turns up in someone's garden.