The United States government detains immigrants under the control of Customs and Border Protection (CBP; principally the Border Patrol) and Immigration and Customs Enforcement (ICE).

According to the Global Detention Project, the United States possesses the largest immigration detention system in the world. As of 2020, ICE detains immigrants in over 200 detention facilities, in state and local jails, in juvenile detention centers, and in shelters. Immigrants may be detained for unlawful/illegal entry to the United States, when their claims for asylum are received (and prior to release into the United States by parole), during the process of immigration proceedings, undergoing removal from the country, or if they are subject to mandatory detention.

During Fiscal Year 2023, 273,220 people were booked into ICE custody. As of FY 2023, the daily average population of non-citizens being detained by ICE was 28,289, however, at the end of the same fiscal year there was a total of 36,845 noncitizens being currently detained. In addition, as of April 2024, roughly 7,000 immigrant children are housed by facilities under the supervision of the Office of Refugee Resettlement's (ORR) program for Unaccompanied Children (UC). For the FY 2023, the ORR reported 118,938 unaccompanied children referrals from DHS to be processed into the UC program. Detention and deportations greatly increased during the second presidency of Donald Trump. By January 2026, the administration would have deported more than 370,000 immigrants.

In mid-February 2026, Reuters reported that in the previous few months, over 400 federal judges had ruled that ICE had illegally detained people a total of 4,421 times, and according to Department of Homeland Security Assistant Secretary Trica McLaughlin, that "President Trump and Secretary Noem were now enforcing the law and arresting illegal aliens who have no right to be in our country and reversed Biden's 'catch and release' policy." The report also stated that thousands of federal court petitions were filed challenging detention, with Reuters reporting more than 20,200 Habeas corpus cases since the president took office.

History Immigration detention in the United States had from 1855 an early facility at Castle Clinton on Manhattan (together with the Marine Hospital on Staten Island for quarantine) and relocated in the 1890s to Ellis Island. It was used as a permanent holding facility for foreign nationals throughout the Second World War, but fell into disuse in the 1950s. In the 1980s, Ronald Reagan reacted to the mass migration of asylum seekers arriving in boats from Haiti by establishing a program to interdict them (i.e. stop and search certain vessels suspected of transporting undocumented Haitians). As the number of illegal immigrants who were fleeing economic and political conditions increased, President Bush Sr attempted to find a regional location to handle the influx. The United Nations High Commissioner for Refugees arranged for several countries in the region—Belize, Honduras, Trinidad and Tobago, and Venezuela—to temporarily provide a safe haven for Haitians, however the Coast Guard was quickly overwhelmed, and by November 18, 1991, the United States forcibly returned 538 Haitians to Haiti. These options also proved inadequate for the sheer numbers of Haitians fleeing their country, and the Coast Guard took them to the U.S. naval base in Guantanamo, Cuba, where they were pre-screened for asylum in the United States.

In 2003, the U.S. Immigration and Customs Enforcement agency (ICE) was created under the Department of Homeland Security. ICE enforces the United States' immigration and customs laws, with the primary role of using investigative techniques to apprehend and detain those suspected of violating them. The Office of Enforcement and Removal Operations (ERO), housed within ICE, carries out "the immigration enforcement process, including the identification, arrest, detention and removal of noncitizens who are subject to removal or are unlawfully present in the U.S."

Process of detention and removal Detained immigrants are given a unique identifying number called an Alien Registration Number ("A-number"), provided they do not already have one by virtue of their legal alien status, and are sent to a county, state, federal, or private prison, where they remain until deported or released after proceedings.

Office of Enforcement and Removal Operations There were four divisions within ICE which work to investigate illegal immigration, enforce immigration laws, and detain and deport offenders of these laws: Enforcement and Removal Operations (ERO), the Office of Investigations (OI), the Office of Intelligence (Intel), and the Office of International Affairs (OIA). ERO is the division that deals directly with the detention of immigrants. ERO, under ICE, operates eight detention centers, termed "Service Processing Centers," in Aguadilla, Puerto Rico; Batavia, New York; El Centro, California; El Paso, Texas; Florence, Arizona; Miami, Florida; Los Fresnos, Texas; and San Pedro, California. ICE also has contracts with seven private companies that run facilities in Aurora, Colorado; Houston, Texas; Laredo, Texas; Tacoma, Washington; Elizabeth, New Jersey; Queens, New York; and San Diego, California. Other facilities that house immigrant detainees include juvenile detention centers and shelters. However, the majority of immigrants are detained in state and local jails, which have contracts with ICE. At the end of the 2007 fiscal year the United States' immigration detention system comprised 961 sites.

As of 2025, ICE had the following 4 divisions, now called directorates: Enforcement and Removal Operations (ERO), Homeland Security Investigations (HSI), Office of the Principal Legal Advisor (OPLA) and Management and Administration (M&A).

Secure Communities

In 2007, the program, Secure Communities, was created within ICE to identify criminal aliens, prioritize them based on the severity of the crimes that they committed, and transform the processes necessary to remove them by increasing efficiency. Secure Communities identifies illegal immigrants with the use of modern technology, notably biometric identification techniques. These were first employed in Houston, Texas in 2008. As of April 2011, the Secure Communities' biometric sharing capability is being used in 1,210 of 3,181 jurisdictions (state, county, and local jails and prisons) in the U.S. Between 2008, when the program was started, through March 2011, 140,396 convicted criminal aliens have been booked into ICE custody resulting in 72,445 deportations.U.S. Immigration and Customs Enforcement: Secure Communities Activated Jurisdictions April 2011. Under the Secure Communities program, the fingerprints of everyone arrested and booked are not only checked against FBI criminal history records, but they are also checked against DHS immigration records. If fingerprints match DHS records, ICE determines whether immigration-enforcement action is required, considering the immigration status of the alien, the severity of the crime, and the alien's criminal history.U.S. Immigration and Customs Enforcement: Secure Communities. Retrieved April 23, 2011. ICE then places a detainer on the individual, which is a request that the jail hold that person for up to 48 hours beyond their scheduled release, so that ICE can come to interview or to possibly take them into custody.Immigration Policy Center: "Immigration Detainers: A Comprehensive Look" February 17, 2010.

The Obama administration has been a big proponent of the program, expanding it from 14 jurisdictions under President George Bush to over 1,210 jurisdictions as of March 2011.Washington Post: "Illegal Immigrant Deportations Up Under Obama" July 26, 2010.New York Times: "Immigration Bait and Switch" August 17, 2010. ICE plans to expand the program nationwide by 2013.U.S. Immigration and Customs Enforcement: Projected Deployment by Fiscal Year of Secure Communities program . Retrieved April 23, 2011.

In a memo dated November 20, 2014, Department of Homeland Security Secretary Jeh Johnson discontinued the Secure Communities program. On January 25, 2017, the Secure Communities program was restarted by the Department of Homeland Security per an executive order signed by President Donald Trump.

Section 287(g) The enactment of the Illegal Immigration Reform and Immigrant Responsibility Act of 1996 added onto the Immigration and Nationality Act a clause, titled Section 287(g), which allows state and local law enforcement officials to enforce federal immigration law on the condition that they are trained and monitored by ICE. This agreement in practice permits local and state enforcement officials to arrest and even detain individuals they encounter during their day-to-day duties if they suspect them to be or "identify" them as illegal immigrants. However, individuals picked up by local law enforcement may have committed minor offenses, such as driving infractions, and lacked proper identification when stopped. Many civil rights groups have accused Section 287(g) of permitting or causing racial profiling.Los Angeles Times: "Tougher Rules on Policing Illegal Immigrants" October 14, 2009.

Detention at the border Often, illegal aliens or individuals lacking legal permission to enter, or remain, in the United States, when apprehended at the U.S. border are detained and placed in removal proceedings in front of an immigration judge. These individuals may include refugees seeking asylum. Under Section 235(b)(2) of the Immigration and Nationality Act, if an individual stopped at the border is believed to be an illegal immigrant or a threat to national security, they are considered "inadmissible" and classified as an "arriving alien." Individuals detained at the border are only released on a case-to-case basis by the authority of ICE officials.

Immigration detention facilities are required to uphold many of the same standards maintained by domestic detention facilities as well as international human rights laws and protocols. Facility officials are prohibited from violating the Eighth Amendment in the utilization of force to cause harm to inmates. The U.S. government has ratified the International Covenant on Civil and Political Rights, the Convention on the Elimination of All Forms of Racial Discrimination, and Convention Against Torture and Other Cruel, Inhuman or Degrading Treatment or Punishment in regards to immigration detention facilities, all of which provide standards and protocols that must be administered and followed in the treatment of immigrant detainees. This includes the proper administration of medical treatment as well as swift response to medical requests by detainees. There have been reports that some facilities utilize punitive disciplinary action that violate the Convention Against Torture and International Covenant on Civil and Political Rights protocols and that abuse by facility officials is not limited to excessive punitive action. The ACLU has reported that complaints of physical, sexual, and verbal abuse by officials are not at all uncommon and state that there seems to be a pronounced lack of response and record keeping of detainee complaints by facility officials. While immigration detention facilities are required to uphold many of the same standards maintained by domestic detention facilities, the biggest discrepancy is in legal representation. Immigrants are not guaranteed a right to due process, but can hire attorneys to handle portions of their casework at cost.

Mandatory detention