America’s high-poverty cities and counties have suffered for decades, enduring skyrocketing inequality, the opioid epidemic, rising housing costs, and widespread disinvestment. Governments have offered a variety of failed solutions, from luring wealthy outsiders to slashing public services. But four communities are turning inward instead: Stockton, California; rural Josephine County, Oregon; Lawrence, Massachusetts; and Detroit, Michigan. In these diverse places—all of …