Since the half of the XIXth century, many reasons encouraged european peoples to migrate to USA ,like war,religious persécution or povrerty ,

the first great wave of immigration was due to the emmigration of the irishs catholics,who migrated to the USA because of the great famine in Ireland,( between 1845 and 1849 )
The irishs settle in the poorest place of the north east of the usa (like the five points in New York) and in the plain of the midwest were the governement gave land to voluntary familys
The Irish were discriminated by the americans protestants ,because they were catholics

The most important contry of emmigration was the germany (over 5 million peoples left germany to USA in less than 1 century ,with a peak in the early 1880's)and they settled in the whole country

The italian emigration is also very important ( about 5 million italian left italia and especialy fled the poverty of the southern italia in 150 years),they stay in the north east and were often stereotyped as being "violent" and "controlled by the mafia"

The religious persecutions is also a reason that drive jew from eastern europe to flee progoms and antisemitism The most recent wave of immigration is due to the fall of the iron curtain. Peoples from the republics of the soviet union migrate to usa to flee war ,dictatorship and communism

some periods of decreasing or increasig immigration can be explain with the history of the USA

From 1861 to 1865 was the American civil war. Eleven Southern slave states declared their secession from the United States.

Since 1897, the gold rush has provoked increasing immigration and developed the economy of the west of the USA.

From 1914 to 1918 was the first world war.-

In 1921 and 1924, the highly decreasing immigration is due to the Johnson-Reed act wich is a quota made for limit the immigarnts to the USA. From 1929 to 1945 there were reasons for the decreasing of the migrations : the great depression of