Over the last sixty years, the courts, Congress, and the President—but mostly the courts—first increased integration in schools and neighborhoods, and then changed course, allowing schools to resegregate. The impact of these decisions is illustrated by the comparative legal histories of Detroit and Louisville, two cities which demonstrate the many benefits of metropolitan-level cooperation on issues of racial segregation, and the harms that arise in its absence. Detroit, Michigan, and Louisville, Kentucky, both emerged from the riots of the 1960s equally segregated in their schools and neighborhoods with proportionally sized racial ghettoes. In 1974-75, the Supreme Court overturned a proposed metropolitan school integration plan in Detroit, but allowed a metropolitan remedy for Louisville-Jefferson schools to stand. Since that time, Louisville-Jefferson schools and neighborhoods, like all the regions with metropolitan plans, have become among the most integrated in the nation, while Detroit’s schools have remained rigidly segregated and its racial ghetto has dramatically expanded. Detroit’s experience is very common in the highly fragmented metropolitan areas of the midwestern and northeastern United States. Black students in Louisville-Jefferson outperform black students in Detroit by substantial margins on standardized tests. Metropolitan Louisville has also grown healthier economically, while the City of Detroit went bankrupt and both the city and school district were taken over by state authorities. The Article concludes with a call to modernize American local government law by strengthening the legal concepts of metropolitan jurisdictional interdependence and metropolitan citizenship.