In September 1950, the U.S. Navy carried out a classified biological warfare experiment off the coast of San Francisco known as Operation Sea-Spray. A Navy vessel released massive quantities of bacteria into the coastal air to study how biological weapons might spread through a major American city. The public had no knowledge that they were part of the test. Military scientists used Serratia marcescens and Bacillus globigii, organisms they believed to be harmless at the time. Sensors placed throughout San Francisco tracked how the particles moved through streets, homes, and public spaces. The test demonstrated that nearly the entire city could be exposed within hours. In the years that followed, concerns emerged after several residents developed rare infections linked to the bacteria used in the experiment. Operation Sea-Spray later became one of the most controversial examples of Cold War biological testing on American populations, raising lasting questions about ethics, secrecy, and government experimentation. https://youtu.be/kKdnfHANogI