High poverty rates, especially among African Americans and Latinos, threaten the well-being of neighborhoods as well as families. We can anticipate that the number of neighborhoods with dangerously high poverty rates is higher today than in 2000, representing a tragic reversal of the downward trend between 1990 and 2000. Historically, public policies played a central role in establishing and enforcing patterns of racial segregation, alongside discriminatory practices by the private sector and individuals. But no single causal process explains the persistence of residential segregation in America today. To ensure the well-being and sustainability of all neighborhoods, public policies must intervene to break the cycle.