The origins of pizza go back to ancient times. Babylonians, Egyptians and other Middle Eastern cultures ate flat, unleavened bread that had been cooked in mud ovens. Mediterranean people such as the Greeks and Romans ate the bread topped with olive oil and native spices.
In the late 1800s, Raffaele Esposito, a baker in Naples, Italy, created pizza as a dish for visiting royalty. According to the story, the Italian King Umberto and Queen Margherita were touring the area. In order to impress them and to show his patriotic fervor, Raffaele chose to top flat bread with food that would best represent the colors of Italy: red tomato, white mozzarella cheese and green basil.
-- adapted from AboutPizza.com