title: A nation of immigrants.
mesh_terms: D000293:Adolescent; D000328:Adult; D001208:Asia; D004641:Emigration and Immigration; D005060:Europe; D006801:Humans; D007878:Legislation as Topic; D008297:Male; D008875:Middle Aged; D009656:North America; D012189:Retrospective Studies; D013020:South America; D014481:United States