Immigration to the United States refers to the process by which foreign nationals enter and take up residence in the country, whether temporarily or permanently. The United States admits immigrants through a statutory framework governing family-based sponsorship, employment-based preference categories, the diversity visa lottery, humanitarian protection (including asylum and refugee resettlement), and various temporary nonimmigrant visa categories. The scope of who counts as an “immigrant,” how immigration levels should be set, and what obligations the state owes to non-citizens are each subjects of ongoing legal, policy, and normative dispute; fuller treatment appears in the viewpoint and debate pages linked below.

The United States receives more lawful permanent residents annually than any other country. The Immigration and Nationality Act of 1965 (Hart-Celler Act) dismantled the prior national-origins quota system and established the family-preference framework that remains the structural basis of legal immigration today. Subsequent major legislation - including the Immigration Reform and Control Act of 1986, the Immigration Act of 1990, and the Illegal Immigration Reform and Immigrant Responsibility Act of 1996 - modified enforcement mechanisms, visa caps, and grounds of inadmissibility without restructuring the underlying preference system.

Estimates of the unauthorized immigrant population have ranged from approximately 10 to 12 million individuals in recent decades, though methodological disputes mean that figures from different sources are not directly comparable. A smaller number of researchers have argued the true figure is substantially higher; that methodological debate is addressed at united-states-america-immigration-unauthorized-population-estimates-debate.

The federal government divides immigration authority across multiple agencies: U.S. Citizenship and Immigration Services (USCIS) adjudicates benefits; U.S. Customs and Border Protection (CBP) manages ports of entry and the border; U.S. Immigration and Customs Enforcement (ICE) conducts interior enforcement; and the Executive Office for Immigration Review (EOIR) within the Department of Justice administers the immigration court system. Significant enforcement and administrative discretion rests with the executive branch, a fact that has produced recurring inter-branch and inter-governmental disputes over the boundaries of that discretion.

Asylum and refugee policy has been a particular site of legal and political contest. The United States is party to the 1967 Protocol Relating to the Status of Refugees and maintains a separate annual refugee admissions ceiling set by the President in consultation with Congress. Rates of asylum grant vary substantially by nationality, adjudicator, and circuit court jurisdiction. Backlogs in the immigration court system have grown to several million pending cases as of the mid-2020s.

State and local governments have pursued divergent approaches to immigration enforcement cooperation, producing a documented landscape of “sanctuary” policies on one end and formal 287(g) agreements with federal immigration authorities on the other. The constitutional boundaries of state and local authority in this domain remain contested in litigation.

Economists across a range of institutions and methodological approaches broadly agree that immigration increases aggregate economic output and that immigrants, as a group, contribute positively to long-run fiscal balances when the full multigenerational arc is measured. There is less consensus on the distributional effects - specifically, which native workers, if any, experience wage or employment displacement, and of what magnitude. See united-states-america-immigration-economic-effects-consensus.

Research in criminology has consistently found that immigrants, including unauthorized immigrants, commit crimes at rates below those of native-born citizens when controlling for relevant demographic variables; this finding has been replicated across multiple independent research teams and data sources. See united-states-america-immigration-crime-rates-consensus.

Multiple distinct viewpoints structure public and scholarly debate over U.S. immigration policy. The following are representative:

• Expansionist / pro-immigration: Immigration levels should be maintained or increased; economic, humanitarian, and cultural contributions of immigrants outweigh costs; enforcement should be humane and narrowly targeted. See United States Immigration - Restrictionist Viewpoint and United States Immigration - Pro Immigration Viewpoint.

• Restrictionist: Current or historical immigration levels are too high relative to the absorptive capacity of labor markets, public services, and civic institutions; reductions in both legal and unauthorized immigration are warranted on economic, cultural, or sovereignty grounds. See United States Immigration - Restrictionist Viewpoint.

• Enforcement-first: Immigration reform should prioritize border security and interior enforcement before any expansion of legal pathways or legalization of unauthorized residents. See United States Immigration - Immigration Enforcement First Viewpoint.

• Legalization / regularization: The unauthorized population already present should be offered a path to legal status; enforcement-only approaches are infeasible and unjust. See United States Immigration - Legalization Viewpoint.

• Open borders: National borders are morally arbitrary; the United States should move toward substantially or fully open immigration as a matter of justice and economic efficiency. See United States - Immigration - Open Borders - Viewpoint.

• Labor-focused restriction: Immigration policy should be assessed primarily through its effects on low-wage native workers; current policy disproportionately benefits employers and high-skilled workers at the expense of less-educated citizens. See united-states-america-immigration-labor-restrictionist-viewpoint.

For structured exchanges between opposing viewpoints, see United States Immigration - Restrictionist Viewpoint and United States America Language Policy - Official English Viewpoint.

• Family separation policy (2017-2018): The Trump administration's “zero tolerance” prosecutorial policy resulted in the separation of thousands of migrant children from parents at the southern border, generating federal litigation, congressional hearings, and international condemnation. See united-states-america-immigration-family-separation-controversy.

• DACA and executive deferred action: The Deferred Action for Childhood Arrivals program, initiated by executive memorandum in 2012, has been the subject of continuous litigation over executive authority, with the Supreme Court ruling in Department of Homeland Security v. Regents of the University of California (2020) against its rescission on procedural grounds while leaving the underlying authority question open. See united-states-america-immigration-daca-controversy.

• Travel ban litigation: Executive orders restricting entry from a set of predominantly Muslim-majority countries generated immediate federal court challenges; the Supreme Court upheld a modified version in Trump v. Hawaii (2018). See united-states-america-immigration-travel-ban-controversy.

• Asylum processing at the southern border: Successive administrations have implemented, litigated, or reversed policies including the Migrant Protection Protocols (“Remain in Mexico”), Title 42 expulsions, and humanitarian parole programs, producing an unsettled legal and policy environment. See united-states-america-immigration-southern-border-asylum-controversy.

• State enforcement laws: Arizona's S.B. 1070 (2010) and similar state-level enforcement statutes prompted litigation over federal preemption; the Supreme Court resolved some questions in Arizona v. United States (2012) while leaving others open. See united-states-america-immigration-state-enforcement-laws-controversy.

• United States America Immigration - History - Historical background
• United States Immigration - Restrictionist Viewpoint - Overview of viewpoints
• united-states-america-immigration-unauthorized-population-estimates-debate - Debate over population estimates
• united-states-america-immigration-economic-effects-consensus - Economic effects consensus
• united-states-america-immigration-crime-rates-consensus - Crime-rate research consensus
• United States Immigration - Pro Immigration Viewpoint - Pro-immigration viewpoint
• United States Immigration - Restrictionist Viewpoint - Restrictionist viewpoint
• United States Immigration - Immigration Enforcement First Viewpoint - Enforcement-first viewpoint
• United States Immigration - Legalization Viewpoint - Legalization viewpoint
• United States - Immigration - Open Borders - Viewpoint - Open borders viewpoint
• united-states-america-immigration-labor-restrictionist-viewpoint - Labor-focused restrictionist viewpoint
• united-states-america-immigration-family-separation-controversy - Family separation controversy
• united-states-america-immigration-daca-controversy - DACA controversy
• united-states-america-immigration-travel-ban-controversy - Travel ban controversy
• united-states-america-immigration-southern-border-asylum-controversy - Southern border asylum controversy
• united-states-america-immigration-state-enforcement-laws-controversy - State enforcement laws controversy
• United States America Language Policy - Official English Viewpoint - U.S. language policy viewpoints (related)

1. Immigration and Nationality Act of 1965, Pub. L. 89-236, 79 Stat. 911 (October 3, 1965). 2. Immigration Reform and Control Act of 1986, Pub. L. 99-603, 100 Stat. 3359 (November 6, 1986). 3. Immigration Act of 1990, Pub. L. 101-649, 104 Stat. 4978 (November 29, 1990). 4. Illegal Immigration Reform and Immigrant Responsibility Act of 1996, Pub. L. 104-208, div. C, 110 Stat. 3009-546 (September 30, 1996). 5. Robert Warren and Donald Kerwin, “The 2,000 Mile Wall in Search of a Purpose: Since 2007, Visa Overstays Have Outnumbered Undocumented Border Crossers by a Half Million,” Journal on Migration and Human Security 5, no. 1 (2017): 124-136. 6. Giovanni Peri, “The Effect of Immigration on Productivity: Evidence from U.S. States,” Review of Economics and Statistics 94, no. 1 (2012): 348-358. 7. National Academies of Sciences, Engineering, and Medicine, The Economic and Fiscal Consequences of Immigration (Washington, DC: National Academies Press, 2016). 8. Michelangelo Landgrave and Alex Nowrasteh, “Criminal Immigrants: Their Numbers, Demographics, and Countries of Origin,” Immigration Research and Policy Brief No. 1, Cato Institute, March 15, 2017. 9. Department of Homeland Security v. Regents of the University of California, 591 U.S. 1 (2020). 10. Trump v. Hawaii, 585 U.S. 667 (2018). 11. Arizona v. United States, 567 U.S. 387 (2012). 12. U.S. Department of Justice, Executive Office for Immigration Review, Adjudication Statistics: Pending Cases, New Cases, and Completions (various years).