Pizza arrived in the United States in the early 20th century along with waves of Italian immigrants who settled primarily in the large cities of the Northeast. It got a boost both in popularity and regional spread after soldiers stationed in Italy returned from World War II.During the latter half of the 20th century, pizza became an iconic dish with considerable acceptance in the United States. Numerous regional variations have evolved, with many bearing only a casual resemblance to the Italian original. It is a popular fast food item produced by many small restaurants as well as several large pizza restaurant chains. The United States pizza restaurant industry was worth $37 billion in 2015.