According to the 2016 Yearbook of Immigration Statistics, the United States admitted a total of 1.18 million legal immigrants (618k new arrivals, 565k status adjustments) in 2016. Of these, 48% were the immediate relatives of United States citizens, 20% were family-sponsored, 13% were refugees or asylum seekers, 12% were employment-based preferences, 4.2% were part of the Diversity Immigrant Visa program, 1.4% were victims of a crime (U1) or their family members were (U2 to U5), and 1.0% who were granted the Special Immigrant Visa (SIV) for Iraqis and Afghans employed by the United States Government. The remaining 0.4% included small numbers from several other categories, including 0.2% who were granted suspension of deportation as an immediate relative of a citizen (Z13); persons admitted under the Nicaraguan and Central American Relief Act; children born after the issuance of a parent’s visa; and certain parolees from the former Soviet Union, Cambodia, Laos, and Vietnam who were denied refugee status.

Between 1921 and 1965, policies such as the national origins formula limited immigration and naturalization opportunities for people from areas outside Northwestern Europe. Exclusion laws enacted as early as the 1880s generally prohibited or severely restricted immigration from Asia, and quota laws enacted in the 1920s curtailed Southern and Eastern European immigration. The civil rights movement led to the replacement of these ethnic quotas with per-country limits for family-sponsored and employment-based preference visas. Between 1970 and 2007, the number of first-generation immigrants living in the United States quadrupled from 9.6 million to 38.1 million residents. Census estimates show 45.3 million foreign born residents in the United States as of March 2018 and 45.4 million in September 2021, the lowest three-year increase in decades.

In 2017, out of the U.S. foreign-born population, some 45% (20.7 million) were naturalized citizens, 27% (12.3 million) were lawful permanent residents, 6% (2.2 million) were temporary lawful residents, and 23% (10.5 million) were unauthorized immigrants. The United States led the world in refugee resettlement for decades, admitting more refugees than the rest of the world combined.

Some research suggests that immigration is beneficial to the United States economy. With few exceptions, the evidence suggests that on average, immigration has positive economic effects on the native population, but it is mixed as to whether low-skilled immigration adversely affects low-skilled natives. Studies also show that immigrants have lower crime rates than natives in the United States. The economic, social, and political aspects of immigration have caused controversy regarding such issues as maintaining ethnic homogeneity, workers for employers versus jobs for non-immigrants, settlement patterns, impact on upward social mobility, crime, and voting behavior.