Italians are usually credited with the development and spread of pizza around the world. Much of that credit is accurate, but the concept of putting stuff on hot bread probably dates back to the days of cavemen. Actual pizza probably made its debut in ancient Greece. The Greeks baked round flatbreads (similar to what we know today as foccacia bread) that they decorated with a variety of spices, seasonings, oils and other toppings.
The word "pizza," meaning "pie," was coined sometime around A.D. 1000 near Rome and Naples, Italy. In the 18th century, flatbread pizza became a popular and cost-effective meal for the peasant population in Naples. People were just beginning to realize that tomatoes, which had been brought over from the New World in the 16th century, were actually not poisonous. By the end of the 18th century, the residents of Naples -- and tourists -- began to top the bread with tomatoes, essentially creating pizza as we know it. Street vendors sold the dish in the poor areas of Naples before the opening of the world's first pizzeria, Antica Pizzeria Port'Alba, in 1830. And pizza is sold today from the very same spot.
Sometime around 1889, Italy's royal couple, Queen Margherita and King Umberto I, toured their kingdom. The Queen took note of the large, flat bread being consumed. She tried it and loved it. She called Chef Rafaelle Esposito to her palace, where he created a variety of pizzas for her. In honor of her, he designed a pizza with toppings in the colors of the Italian flag (red tomatoes, white mozzarella and green basil). This pizza became her favorite and is known to this day as the Margherita. Her love for pizza made her incredibly popular among her subjects -- most royals would never have dined on peasant food, much less encourage its spread [source: A Full Belly].
Pizza appeared on the American scene quietly in the late 19th century with the mass arrival of Italian immigrants. It was mostly sold on the streets of large Italian neighborhoods in such cities as Philadelphia, Chicago and New York City. Pizza soon became available in cafes and grocery stores, but it pretty much remained exclusive to Italian neighborhoods until after World War II. At this time, soldiers returning from Italy increased demand for the dish. Pizza's popularity spread like wildfire, and pizzerias began popping up all over the United States, followed quickly by chain restaurants like Shakey's Pizza and Pizza Hut.