Throughout Europe there are many similar pies based on the idea of covering flat pastry with cheese, meat, vegetables and seasoning such as the Alsatian flammkuchen, German zwiebelkuchen, and French quiche.

Pizza was brought to the Trenton area of New Jersey with Joe's Tomato Pies opening in 1910, followed soon by Papa's Tomato Pies in 1912. In 1936, De Lorenzo's Tomato Pies was opened. While Joe's Tomato Pies has closed, both Papa's and Delorenzo's have been run by the same families since their openings and remain among the most popular pizzas in the area. Frank Pepe Pizzeria Napoletana in New Haven, Connecticut, was another early pizzeria which opened in 1925 (after the owner served pies from local carts and bakeries for 20–25 years) and is famous for its New Haven–style Clam Pie.