Virtually all historical research on immigrants and crime concerns domestic crime. Questions about immigrants and international (or transnational) crime have been left largely unexplored. Important work on domestic crime appeared from 1880 to 1945, including the efforts of the Dillingham and Wickersham Commission. Other early analyses concerned immigrant involvement in the white slave trade (human trafficking), anarchist violence (terrorism) and drug trafficking. The League of Nations carried out important research using undercover researchers and developing concepts such as the “international underworld.” Private organizations such as the Bureau of Social Hygiene and the International Narcotic Education Association played a vital role as well. Although historical research does not generate the same sorts of policy recommendations as social science research, historical knowledge makes an essential contribution to the understanding of ethnicity, crime, and immigration.