From the American takeover of California in 1846 during the U.S.-Mexico War to Police Commissioner Jesse B. Cook's nationwide law enforcement advisory tour in 1912 and San Francisco's debut as the jewel of a new American Pacific world during the Panama Pacific International Exposition in 1915, San Francisco's culture of popular justice, its multiethnic environment, and the unique relationships built between informal and formal policing created a more progressive policing environment than anywhere else in the nation. Originally an isolated gold rush boomtown on the margins of a young nation, San Francisco--as illustrated in this untold story--rose to become a model for modern community policing and police professionalism.