Conditions at the US government's immigrant detention facilities have come under fire in recent days after new reports of overcrowding and insufficient supplies.

The Department of Homeland Security's inspector general reviewed a set of five facilities in June and released harrowing pictures suggesting severe overcrowding. Court documents from migrants seeking asylum filed in California paint a picture of inadequate food and water, freezing temperatures, and a lack of proper bedding.

The freshman Rep. Alexandria Ocasio-Cortez ignited a firestorm on Twitter by referring to the facilities as "concentration camps." Ocasio-Cortez then called the conditions at an El Paso, Texas, Border Patrol facility she toured "horrifying," saying migrants were subjected to psychological abuse and told to drink out of toilets.

In late June, several leading Democratic presidential candidates (including Sens. Elizabeth Warren, Amy Klobuchar, and Kamala Harris and Mayor Pete Buttigieg of South Bend, Indiana) visited a detention center for child migrants in Texas to protest conditions at the facilities.

How the US detention policy has changed over time

Under a policy that started in early 2018, the administration of President Donald Trump has separated more than 2,300 children from their parents at the US-Mexico border. Former Attorney General Jeff Sessions instructed the Department of Homeland Security to institute a "zero tolerance" policy seeking prosecution of every migrant suspected of crossing the border illegally.

When border officials capture a family trying to enter the US outside a recognized port of entry, the agents arrest the migrants and take them to a Customs and Border Protection holding facility for processing. If they want to seek asylum, adults are then sent to Immigration and Customs Enforcement detention centers, while kids are transferred to shelters. Here, the children wait to see whether they will be deported or reunited with relatives in the US — if the government or a nonprofit can find them.

Because of mounting political pressure, Trump signed an executive order in June 2018 that he said would end the family separation (while keeping the "zero tolerance" regulations). The fate of children already in custody is unclear, however, and the order faces legal challenges.

As of November 2017, according to a Freedom of Information Act request filed by the nonprofit National Immigrant Justice Center, ICE operated 1,478 adult detention centers — a number that doesn't include the CBP facilities, which are all within 100 miles of the southern border.

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ICE has published a limited map of these facilities, which also doesn't include the hundreds of county jails, Bureau of Prisons facilities, Office of Refugee Resettlement centers, hotels, and hospitals the agency contracts with. (To see the complete list with addresses, head over to the Immigrant Legal Resource Center's site.)

We created the above map showing the number of ICE detention facilities in every US state (plus Puerto Rico and Washington, DC) as of November 2017.

Many of the facilities are hiding in plain sight

As the above map shows, every state had at least two facilities where ICE detained immigrants. Border states like Texas and California had the most detention centers. Small states like Delaware, Hawaii, and Rhode Island had the fewest. There were ICE-operated facilities in Alaska, the largest state by land area.

Many of these facilities are hiding in plain sight near major urban centers. In Brooklyn, New York, there's one next door to an Ikea. The facility with the most detained immigrants (1,917 people as of late 2017) was the Stewart Detention Center, a private prison in Lumpkin, Georgia.

In November 2017, ICE reported that its total average daily population for the 2018 fiscal year was 39,322 people, marking the second year in a row that figure had reached a record high.

As the National Immigrant Justice Center notes, on an average day in November 2017, ICE held most people — 71% of the total — in prisons operated by private companies. Since 2012, every authorized ICE facility has passed every government inspection, even those where multiple people have died, with some deaths later reported a result of medical neglect.

ICE categorized the majority of incarcerated immigrants — 51% on average — as "non-criminal" and as posing "no threat." Twenty-three percent were designated as the lowest "Level 1" threat, which typically includes people with nonviolent criminal convictions. Just 15% were classified at the highest threat level.