In the mid-1800s, large numbers of immigrants crossed the Atlantic Ocean to begin new lives in the United States. More than 4 million of them settled in the United States between 1840 and 1860, most from Europe. More than 3 million of these immigrants arrived from Ireland and Germany. Many of them were fleeing economic troubles in their native countries. Some were seeking political or religious freedom.

Fleeing the Irish Potato Famine
In the mid-1840s, potato blight, a disease that causes rot in potatoes, left many families in Ireland with little food. More than a million Irish people died of starvation and disease. Even more fled to the United States.
Most Irish immigrants were very poor and settled in northeastern cities to look for work. By 1850, the Irish made up one fifth of the population in seven major cities, including New York, Philadelphia, and Boston. They worked at unskilled jobs in the cities or on Most Irish immigrants were very poor and settled in northeastern cities to look for work. By 1850, the Irish made up one fifth of the population in seven major cities, including New York, Philadelphia, and Boston. They worked at unskilled jobs in the cities or on building canals and railroads. Irish women often worked as domestic servants forwealthy families, laboring 16 or more hours per day. In 1849, a Boston health committee reported that low wages forced most Irish immigrants to live in poor housing.
Still, many immigrants enjoyed a new feeling of equality. Patrick Dunny wrote home to his family saying, "that cuts a great dash [style) at home... think it strange [in the United States) for the humble class of people to get as much respect as themselves."

In three sentences How is the Background more or lass useful when researching immigration in the 1800s?

The background information about large numbers of immigrants crossing the Atlantic Ocean to settle in the United States in the mid-1800s provides context for understanding the scale and significance of immigration during that time period. Knowing that over 4 million immigrants settled in the United States between 1840 and 1860, with the majority coming from Europe, helps to highlight the magnitude of this movement. Additionally, understanding the reasons behind their migration, such as fleeing economic troubles or seeking political and religious freedom, sheds light on the motivations and experiences of these immigrants.