The California Gold Rush leads to San Francisco’s “rapid monstrous maturity” into a major metropolis. Establishing the infrastructure to support the instant city means radical change for San Francisco Bay. By century’s end, San Francisco Bay is the center of a broad economic empire on the Pacific. • Gold Fever: The Bay Welcomes the World • Imperial San Francisco: The Emerging Bay Empire • Bay Fishery: Salmon, Striped Bass and Tales of the Fish Patrol • Invasion!: The Coming of the Transcontinental Railroad Introduces New Species