ProPublica’s “Zero Tolerance” series on the Trump administration’s immigration policy at the border won this year’s George Polk Award in Journalism in the immigration reporting category. Administered by Long Island University, the Polk Awards honor intrepid and influential work, with a premium placed on original and resourceful investigative reporting. This marks the seventh Polk Award for ProPublica.

The series launched in June 2018, minutes before a scheduled White House press briefing about the Trump administration’s family separation policy, when ProPublica published an audio clip that captured the sounds of children recently separated from their families at the Mexican border. The recording of children sobbing and begging for their parents rippled through the briefing room. When Kirstjen Nielsen, Secretary of Homeland Security, arrived, reporters peppered her with questions about the recording.

The cries were played by lawmakers on the floors of Congress, and by protesters at demonstrations across the country. Within 48 hours of ProPublica’s publication, President Donald Trump signed an executive order to end the policy and keep immigrant families together. A federal judge in California ordered that parents and children be reunited within 30 days.

ProPublica then mobilized to dig deeper into how children had been affected. Reporters on many beats — in our newsrooms in New York and Chicago — pitched in and filed public records requests for police reports and call logs concerning more than 100 shelters for immigrant children nationwide. This brought to light for the first time hundreds of allegations of sex abuse, fights and missing children, upending the Trump administration’s assertions that the shelters were safe havens. Arizona’s governor ordered a statewide inspection, leading to the shutdown of two centers run by Southwest Key after the nonprofit failed to provide proof that its employees had completed background checks. Following these stories and coverage by other media outlets, top Republican and Democratic senators demanded an investigation, and the U.S. Health and Human Services Department’s inspector general is now investigating employee background checks and the treatment of children in the nation’s shelter system.

In addition to ProPublica’s stories about shelters for immigrant children, revealing systematic crimes and abuses that authorities had either ignored or covered up, we were the first to map the vast system of these shelters across the country. We anchored a partnership of 10 newsrooms across four countries, soliciting and fielding tips in English, Spanish and Portuguese that led to the reunification of at least four families.

Zero tolerance was first and foremost a policy aimed at children, and ProPublica focused its reporting on the experiences and voices of children. Even when we didn’t have direct access to the children, or when they were too young to make sense of what they were going through, our reporters followed them through the system by tracking down their parents, as well as the lawyers, social workers and foster parents who were with them along their journeys. This allowed us to explain what they said and did during their time in the United States immigration system. Ginger Thompson, Michael Grabell, Topher Sanders, Adriana Gallardo, Melissa Sanchez, Duaa Eldeib, Jodi S. Cohen, Alex Mierjeski, Claire Perlman, and Ken Schwencke, Decca Muldowney, Derek Kravitz, Lilia Chang, Rachel Glickhouse and María Sánchez Díez contributed to the series.

See a list of all this year’s Polk Award in Journalism winners here.