Okay, so a long time ago, around 1944, there was a place called Port Chicago, where lots of boats would come in and out to get loaded up with bombs and other dangerous stuff.
One day, there were some sailors who were in a big hurry to load up one of those boats with bombs. They were working really fast, even though they didn't have any special training on how to handle all those explosives safely!
Well, unfortunately, something went wrong. There was a huge explosion, and it was so loud and powerful that it was felt from miles away. The explosion was so strong that it even knocked people over and broke glass windows!
Sadly, over 300 people died because of this disaster, and a lot of them were African American sailors who were working there. It was a really tragic event, and people tried to make sure that it never happened again by making new safety rules for handling dangerous materials like bombs.