Immigrants who came to the United States during the late 19th and early 20th centuries generally came for economic opportunities or to escape from difficult environments in their home countries.
Many immigrants came to the U.S. to better themselves economically. Those who arrived from all over Europe had typically lived in poverty in their home countries or were removing themselves from crisis situations. For example, in the 1840s, Irish immigration peaked during the Irish famine, and almost 50 percent of immigrants to the U.S. were from Ireland. It's estimated that between the years of 1820 to 1930 around 4.5 million Irish people in total moved to the U.S.
Another large group of people to immigrate to America were the Germans. They, too, were affected by the potato blight that hit Ireland in the 1840s. After the American Civil War until the 1870s, many farm workers came to get away from unemployment in Germany and the industrial economic depression and resulting unrest in that country. Many Germans made the journey to the Midwest, and a large percentage (nearly 50 million) of U.S. citizens are descended from those original German immigrants.
Chinese immigrants came for jobs on the railroads in the western U.S. They also joined in the California gold rush and other opportunities throughout the land, including labor for industry. Most of them came from poor agricultural backgrounds and were looking to earn money to send to their families in China. Some intended to return home but many ended up staying in the United States.
Religious persecution was another driver of immigration. Scandinavian immigrants fled official discrimination in their home countries while Russian Jews came to America to escape the pogroms. The assassination of the Tsar Alexander II in 1881 ignited anti-Jewish riots and resulted in systematic government persecution in Russia. Germans also experienced religious persecution in their home country when Lutherans split from the main Protestant Evangelical Church of the Prussian Union.
During the early 1900s, Italy experienced a number of natural disasters including the eruption of Mount Vesuvius, an earthquake and a tidal wave. These all happened in the south of Italy, where government involvement and assistance was very poor and the population mainly lived in the rural areas. The ship fare to America was now affordable, so many southern Italians left for the U.S. Often, the adult and older teen males in the family would travel first, get settled and then send money home for the women and children to join them.
People who arrived from Europe entered via the East Coast, with more than 70 percent coming in through New York. The Ellis Island processing center was opened in 1892 to cope with the influx of people arriving from the Old World. Asian immigrants arrived on the West Coast of the U.S., coming in at various ports.
Around 20 million people immigrated to the United States from 1880 and 1920. The peak year was 1907, when it's estimated 1.3 million immigrants arrived legally in the U.S. From then, immigration figures declined due to stricter regulations such as literacy testing, quota systems according to where people came from and the outbreak of World War One.