I was excited to learn that two of my favorite things, New York City and gum, have a bit of shared history. Here's the short version: 

In 1869, General Santa Anna, eleven-time former President of Mexico, was exiled in Staten Island, staying with Thomas Adams, a former photographer he had met decades before. 

Santa Anna thought chicle could be mixed with rubber to make cheaper tires and suggested it to Adams as a business venture. A ton of chicle was shipped up to New York, and Adams began experimenting--and failing.

With nothing left to lose, he decided to try using chicle as a gum base, knowing it was chewed this way in Mexico. At the time, most commercial gums in the US were made of paraffin, so this was a pretty neat new thing. 

What's chicle? It looks like that stuff in the photo above, and it's best described by our good friend Harold McGee, from On Food and Cooking: 

"Chicle is a latex, a milky, water-based plant fluid that carries tiny droplets of long, coiled carbon-hydrogen chains. These chains have the properties of being elastic: they uncoil and stretch out when pulled, but snap back when released. The best known of these latex substances is rubber."

Needless to say, it was a hit. 

Nowadays, chicle is hard to come by and expensive, so gum today is made of things that come from the lab, rather than a tree. It actually contains some of the same substances that go into tires and paints. Neat. 

If you chew sugar-free gum, you'll be happy to know that Xylitol, the gum's sweetener, is good for reducing plaque on your teeth. I had always thought the act of chewing gum was helpful because it kinda scrubbed your teeth, but turns out there's more to it!

The bacteria that make plaque need fermentable sugar, like sucrose, to survive. Xylitol is kinda similar in structure to sucrose, so it attracts the bacteria, but it turns out they can't eat it, so they end up dying. Xylitol is crafty like that. 

If you want to know way more about gum, check out these sources:
http://en.wikipedia.org/wiki/Xylitol
http://www.ilovegum.com/Story.html
On Food and Cooking