Italian immigration to the United States has contributed significantly to the country's population, with Italians representing as much as 10 percent of the foreign population in some decades. The reasons varied across time, with economic depression, social unrest and even natural disaster motivating emigration from Italy. Until the 1950s, Italian immigration went through various waves, reaching a height around the turn of the 20th century and declining thereafter.

Pre-Civil War

From the American Revolution until the Civil War, Italian immigration to the United States was light. Many immigrants during this period tended to be well-off artists, missionaries, teachers or other professionals. Most immigrants were from northern Italy. These wealthy professional immigrations, however, were few in number. The high point of Italian immigration before the Civil War came in the 1850s, and even then only 9,231 Americans recorded an Italian region as their place of birth. This number paled in comparison to the number of Italians who arrived in the U.S. in subsequent decades. Furthermore, many of these early immigrants might not have self-identified as "Italian," because Italy was not a unified state until the 1860s.

Late 19th Century

Italian immigration to the United States picked up considerably beginning in the 1870s. In that decade, 55,759 Italians immigrated to the United States. In the following decade, 307,309 arrived, and arrivals only increased from there. Most immigrants from this period, unlike their predecessors, arrived from southern Italy. Population pressures in Italy motivated their emigration: In the 1870s, birth rates rose while death rates declined, and crowding became a problem in Italy. Agricultural land became scarce, and Italy lacked the natural resources such as coal that were needed to industrialize. Furthermore, northern Italians dominated Italy's government, and many southerners found this oppressive.

1900s to 1924

The first two decades of the 20th century witnessed the peak of Italian immigration to the United States. From 1900 to 1910, more than 2.045 million immigrants arrived, and from 1910 to 1920 another 1.11 million immigrated. Poverty, political oppression and violence in southern Italy continued to motivate immigration in this period. In addition, natural disasters wreaked havoc on southern Italy in the first decade of the 20th century. Two volcanoes -- Mount Vesuvius and Mount Etna -- erupted in short succession and buried towns near Naples. In 1908, an earthquake triggered a tidal wave and killed more than 100,000 in the city of Messina alone. These disasters further weakened southern Italy's economy and contributed to immigration.

National Quota Act to 1950s

By the 1920s, however, Italians began to face significant discrimination in the United States. As early as 1891, a mob lynched Italians in New Orleans despite their being found not guilty of murdering the city's police chief. Anti-immigrant sentiment expanded to all immigrant groups, and in 1924 Congress passed the National Origins Quota Act, which limited a country's immigration allowance to 2 percent of that country's presence in the U.S. in 1890. Later in 1929, a new National Origins Act was adopted that further limited immigration. This vastly reduced Italian immigration to the U.S. until after the 1950s, when immigration laws were changed.