La Storia traces the history of the approximately 4.5 million immigrants who left Italy for the United States. The authors present a brief history of Italian immigration in the colonial period (starting with Columbus himself). They then cover the factors that led to mass immigration from Italy following the unification of the country in 1871. After the unification, the southern part of the country, called the Mezzogiorno, was given a less favorable status than the northern part of the country. The poverty of the South and its inferior status relative to the North were some of the factors that led Italians to immigrate in mass numbers to the United States.

The authors describe what it was like for Italians to leave their homeland and the ways in which they were received in the US. After their arrival, Italian immigrants often realized that many of the myths of America were just that—myths—and they lived in poverty and in crowded conditions. The authors examine the Italian immigration not just to New York but also to New Orleans and to California, where Italians often worked as fishermen. The authors also examine the process of Italian assimilation in the United States. They write about how organized crime was not characteristic of the first generation of Italian immigrants but was something their children developed as they were assimilated into American culture (though, to the dismay of Italian Americans, organized crime is still widely and falsely regarded as an entirely Italian creation).

The authors examine the movement of Italian Americans from socialism to the participation in labor unions to improve their working conditions. They also look at how Italian Americans' cultural tastes have changed with assimilation and note Italian Americans' success in the worlds of sports, literature, politics, business, and film. In the last section, the authors examine the post–World War II period. In the epilogue, they discuss the ways in which Italian Americans have been divided into a professional class comprised of about 20% of Italian Americans and into a working class comprising everyone else. They note that this pattern has replicated the situation in Italy that drove many people to emigrate from their homeland in the first place.