North Carolina’s Cape Fear River is a massive water system. It stretches across the lower half of the state, collecting runoff from 29 counties and providing water to millions of people. But in the city of Wilmington, where the river meets the Atlantic Ocean, the water has residents worried. In a 2019 test of tap water, Wilmington and neighboring Brunswick county were among the top five areas for high levels of PFAS, or per- and polyfluoroalkyl substances — a group of man-made chemicals commonly used for making nonstick or water-resistant products. Now North Carolina is reckoning with the legacy of pollution upstream — and discovering what decades of PFAS contamination means for the rest of the country.