Project 112 was a secret, cold-war era project to determine vulnerabilities of US warships to various chemical and biological attacks. While lots is known about what happened, there’s still a lot of information that hasn’t been released yet.
In the early 1950s, the US Army sprayed the bacteria Serratia Marcesens over San Francisco. While the government thought that it was safe, many people ended up checking into the hospital. One elderly man even died as a result of the US testing chemical and biological agents against it’s own citizens. [metafilter.com]