While certainly ancient, the earliest origins of pizza are not at all
clear. One interesting legend recounts that the Roman soldiers
returning from Palestina, where they had been compelled to eat
matzoh among the Palestinian Jews, developed a dish called
picea upon gratefully returning to the Italian peninsula.

Most sources, however, agree that an early form of pizza
resembling what today is called focaccia was eaten by many
peoples around the Mediterranean rim, e.g., by Greeks,
Egyptians etc.

These dishes of round pita-like, cooked bread with oil and spices
on top are the ancestors of pizza, but are not properly speaking
pizza. The tomato was unknown and the Indian water buffalo had
not yet been imported to Campania, the area around Naples.

With the discovery of the New World, the tomato made its way to
Italy through Spain. It was considered a poisonous ornamental
and so in the first centuries of its import was not eaten.

The Neapolitan people seem to be the first to wholeheartedly
adopt the tomato into their cuisine, so that in our day the (plum)
tomato is the most characteristic element of Neapolitan cuisine.

Over the centuries, a veritable tradition of pizza was developed
among the Neapolitan poor. It is not surprising, then, that a
modern pizza, that is, with mozzarella di bufala and tomato was
made in 18711 in Naples for Princess Margherita of Savoia by
Raffaele Esposito. This patriotic pizza, of basil, tomato and
mozzarella, in honor of the new tricolor Italian flag's red, green
and white, became the pizza alla Margherita. This form of pizza
was then made known,  popularized and adapted in all the world
through waves of emigration from Naples in the late 19th and
early 20th centuries.

The History of the American style pizza pie.

The United States is among the most pizza enthusiastic
countries one can find today. How did this come about?

Italian immigrants to New York City began making a version of
pizza when they arrived in their new American home at the turn of
the 20th century. The first pizzeria in the U.S. was opened by an
Italian immigrant in 1905.

In addition, American GI's returning from Italy gained a familiarity
with the dish and it is in the post-WWII period that pizza really
takes off in the United States.