PSA: Illicit fireworks rattle NYC. I know it's American tradition, and we're all desperate for some jubilation, but if folks knew the grim colonial-racist history, they'd be less inclined to see fireworks as celebratory. Remedial history with a dash of science below. #4thofJuly (2) The primary gunpowder in fireworks is potassium nitrate, commonly known as saltpeter. In the young United States, saltpeter was imported from the British India colonies.