Introduction : a police-centered story of juvenile justice -- 1. Competing ideas of delinquency -- 2. Growing up and getting in trouble in turn-of-the-century Detroit -- 3. Juvenile justice before juvenile court : Detroit, 1890-1908 -- 4. The widening net of juvenile justice, 1908-19 -- 5. Police in the service of Chicago's "court of last resort" -- 6. The rise of police crime prevention, 1919-40 -- 7. Shifting priorities : targeting serious crime and minority youth in interwar Los Angeles -- 8. Saving young offenders or getting tough on juvenile crime? Police and the expanding network of juvenile justice