Immigration, or the migration of a people into a country, along with its correlative emigration, or the migration of a people out of a country, constitutes a most important social phenomenon. All peoples seem more or less migratory in their habits. Man has been a wanderer upon the face of the earth since the earliest times. According to modern anthropology the human species probably evolved in a relatively narrow area and peopled the earth by successive migrations to distant lands. In all ages, therefore, we find more or less migratory movements of populations. But the movements in modern times, particularly in the nineteenth century, probably exceed, in the number of individuals concerned, any other migratory movements of which we have knowledge in history. Ancient migrations were, moreover, somewhat different from modern immigration and emigration. Ancient migrations were largely those of peoples or tribes, while in modern times migration is more of an individual matter. The Huns, for example, came into Europe as a nation, but the immigration into the United States at the present time is wholly an individual movement. The causes of migration are more or less universal, but corresponding to the difference in ancient and modern migrations we find the causes varying somewhat in ancient and modern times. The causes of ancient migrations and the primary causes of all migrations seem to be: (1) lack of food; (2) lack of territory for an expanding population; (3) war. In modern times we find other causes operating, like, (4) the labor market; men now migrate chiefly to get better economic opportunities; (5) government; in modern times the oppression of unjust governments has often caused extensive migration; (6) religion; religious persecution and intolerance have in modern times been important among the causes of migration.