Greek Origin
While pizza is certainly most closely associated with Italy (and, by proxy, New York City), it was actually invented by the Greeks. Always a fan of using flat breads, they were the first to bake these breads and spread oil, vegetables, and spices on top. While this may not sound exactly comparable to what you get delivered today, it was almost certainly the first step towards the dish we know today. Italy, however, was the first country to open a pizzeria, which happened in the 18th century.
Cheese
While it's hard to imagine pizza without cheese today, it wasn't until 1889 that this indispensable topping was added. An Italian chef was commissioned to create a masterpiece for the visit of Queen Margherita. His innovations included adding cheese, tomato sauce, and basil, each of which represented one of the colors on the Italian flag. Now, of course, this particular version is known popularly as Margherita pizza, and most of the common pies we eat are derivations of this concept.
Pepperoni
Taking cheese as a staple ingredient, pepperoni is by far the most popular pizza topping in the United States. Nearly a third of all pies sold in America have pepperoni included, which makes the meal one of the country's most enduring and widespread. Of course, this has in turn led to popular sales of the meat in grocery stores and other food outlets, as people either adapt it to other meals, eat it as a snack, or use it to make their own pies at home.
Crust
While there is no question that Chicago style deep dish has made a substantial impact on pizzerias around the world, the large majority of people still order and prefer a thinner crust. This doesn't necessarily mean the thin, bark-like crust endorsed by some popular chains, but certainly thinner than the thick, nearly cake-like variety so popular on the banks of Lake Michigan.
