The first immigrants to the territory now the United States were from Western Europe. The first great migration began early in the 19th century when large numbers of Europeans left their homelands to escape the economic hardships resulting from the transformation of industry by the factory system and the simultaneous shift from small-scale to large-scale farming. At the same time, conflict, political oppression, and religious persecution caused a great many Europeans to seek freedom and security in the U.S.
The century following 1820 may be divided into three periods of immigration to the U.S. During the first period, from 1820 to 1860, most of the immigrants came from Great Britain, Ireland, and western Germany. In the second period, from 1860 to 1890, those countries continued to supply a majority of the immigrants; the Scandinavian nations provided a substantial minority. Afterwards the proportion of immigrants from northern and Western Europe declined rapidly.
In the final period, from 1890 to 1910, fewer than one-third of the immigrants came from these areas. The majority of the immigrants were natives of Southern and Eastern Europe, with immigrants from Austria, Hungary, Italy, and Russia constituting more than half of the total. Until World War I, immigration had generally increased in volume every year. From 1905 to 1914 an average of more than a million immigrants entered the U.S. every year. With the start of the war, the volume declined sharply, and the annual average from 1915 to 1918 was little more than 250,000. In 1921 the number again rose; 800,000 immigrants were admitted. Thereafter the number declined in response to new conditions in Europe and to the limitations established by U.S. law.
The first measure restricting immigration enacted by Congress was a law in 1862 banning American vessels from transporting Chinese immigrants to the U.S.;...