On Sept. 28, 1918, the Naval Reserve Station at Los Angeles Harbor was placed under quarantine as a precautionary measure for influenza.

Several days later, Army officials placed the Arcadia Balloon School under protective quarantine, prohibiting the men there from visiting nearby Pasadena and other communities without special permission.

The first civilian cases in Los Angeles appeared on September 22, although influenza was not made a reportable disease in California until September 27.