Every 4th of July, many Americans celebrate their nation's independence with barbecues, family, and a fireworks display. Whether it’s a few small poppers ignited in the backyard or an elaborate show at a local park, lighting up the night sky with color and sound has become a tradition—not only for Independence Day, but sporting events and other public gatherings as well.
If you’re curious about where fireworks come from, how they became associated with holidays, and when consumers go a little too big, we’ve got your primer here.
1. Fireworks originated in ancient China.
You need to turn back quite a few pages in the history books to find the origin of fireworks. As best as anyone can tell, the explosive amusement was developed in the 2nd century BCE in Liuyang, China. Bamboo sticks thrown into bonfires would make a “pop” noise when the air inside the bamboo's cavities heated up. (Baozhu, the Mandarin word for firecracker, means “exploding bamboo.”)
Sometime between 600 and 900 CE, a mix of potassium nitrate, sulfur, and charcoal—saltpeter, or rudimentary gunpowder—was poured into bamboo or paper tubes. When ignited with burning tissue paper, they caused an even bigger bang. The addition of steel or cast-iron shavings to the saltpeter made them sparkle. Old iron pots would also be crushed into sand and mixed with gunpowder. The Chinese used these to commemorate births, deaths, and other occasions. By the 15th century, Europeans were using the mixtures to celebrate both religious and secular events.
2. Fireworks were part of the very first 4th of July celebration.
Fireworks weren't an afterthought of the 4th of July holiday—they were there all along. During the country’s first Independence Day celebration in Philadelphia in 1777, revelers set off a number of explosions from cannons and firearms, honoring John Adams’s belief that the day should be marked by cannons, bonfires, and illuminations. When the displays of ammunition eventually declined—they were not exactly safe for the public—fireworks took over, forever marking the day as the premier reason to strike a fuse.
3. Metallic compounds give fireworks their different colors.
Whether they're Roman candles or falling leaves, fireworks share the same underlying science. Rocket fireworks consist of a mortar, a fuse, propellant powder, a shell, a bursting charge, and pellets known as “stars.” When the fuse is lit, a lifting charge fires the shell out of the mortar and into the air. Once in the air, a time-delay fuse triggers a second explosion and bursting charges release the stars, which contain metallic compounds that give fireworks their color. Each compound has a different shade when ignited: Magnesium is white, copper is blue, sodium is gold, and so on. The style or design of the fireworks display depends on how the stars are arranged inside the shell.
4. Not all fireworks shoot skyward.
Fountain-style fireworks remain on the ground and shoot sparks out of a paper mortar. Catherine wheels are fountains arranged in a ring attached to a pole; when they're lit, the thrust of the fountains causes the ring to spin. Sparklers are simply wires coated in metallic fuel (aluminum or magnesium), oxidizer, and binding material that will burn and then fizzle.
5. There’s a trick to how fireworks can change colors in mid-air.
How can fireworks actually shift their shade in mid-air? It’s pretty simple. The stars, or pellets, are coated in multiple metal salts. After burning through the outer layer—like magnesium, giving off white sparkles—the second layer is ignited, emitting a different hue.
6. One state has totally banned consumer fireworks.
Because fireworks can be dangerous, disruptive, or both, some states have laws on the books limiting their use. Illinois, Ohio, and Vermont permit only wood or wire stick sparklers. And if you live in Massachusetts, you’re completely out of luck—no fireworks of any kind are allowed to be used by consumers. Professional displays are still OK, however. On the other hand, Missouri, Pennsylvania, South Carolina, and Texas have relatively lenient regulations for consumer-grade fireworks.
Some states, like Indiana, mandate that fireworks can be used only between 9 a.m. and 11 p.m. on non-holidays. For the 4th of July, Memorial Day, or New Year’s Eve, you can go wild and set them off until midnight.
7. Legal fireworks give you enough time to get out of their way.
What makes fireworks legal or illegal? The Consumer Product Safety Commission (CPSC) instigated a "fuse burn time" standard that legal fireworks need to meet. Typically, consumer-grade fireworks must have a fuse burn time of between three and nine seconds so users can get away from the fireworks before they go off. Legal fireworks are also limited to containing 50 milligrams of pyrotechnic material.
8. San Diego accidentally set off all its fireworks at once.
In one of the more memorable public fireworks displays, the city of San Diego, California, had a mishap during their 4th of July celebration in 2012. The annual Big Bay Boom fireworks show was supposed to take place over 18 minutes, with a carefully orchestrated series of detonations. Instead, thanks to a computer error, it went off in just 15 seconds.
9. The world’s largest firework weighed over 2 tons.
In February 2020, the world’s largest aerial firework went off. Weighing in at 2797 pounds, or roughly the weight of a four-door sedan, it detonated over Steamboat Springs, Colorado, for the city's Winter Carnival after being ejected by a tube at 300 miles per hour. It set a Guinness World Record in the process. You can view the apocalyptic footage above.