In 1910, the Baltimore City Council passed the nation’s first racial-zoning law. It was not the city’s first effort to eliminate even the possibility of racially integrated neighborhoods. In fact, the movement in favor of residential-segregation ordinances was a response to (its proponents believed) the school system’s failure to use Jim Crow schools to create Jim Crow neighborhoods. The Supreme Court invalidated housing segregation laws like Baltimore’s in 1917, but they turned out to be forerunners of all the other tools generations of city officials, white property owners, and realtors used and still use to maintain racially homogeneous neighborhoods nationwide—like exclusionary zoning. Thanks to these public policies, and to the still segregated schools that inspired them, American cities today are sorted beyond the wildest imaginings of any Progressive-era segregationist.