United States Biological Weapon Testing

The United States biological weapons program officially began in spring 1943 on orders from U.S. President Franklin Roosevelt. Research continued following World War II as the U.S. built up a large stockpile of biological agents and weapons. Over the course of its 27-year history, the program weaponized and stockpiled the following seven bio-agents (and pursued basic research on many more):

Throughout its history, the U.S. bioweapons program was secret. It became controversial when it was later revealed that laboratory and field testing (some of the latter using simulants on non-consenting individuals) had been common. The official policy of the United States was first to deter the use of bio-weapons against U.S. forces and secondarily to retaliate if deterrence failed. There exists no evidence that the U.S. ever used biological agents against an enemy in the field (see below for alleged uses).

In 1969, President Richard Nixon ended all offensive (i.e., non-defensive) aspects of the U.S. bio-weapons program. In 1975 the U.S. ratified both the 1925 and the 1972 Biological Weapons Convention (BWC)—international treaties outlawing biological warfare. Recent U.S. biodefense programs, however, have raised concerns that the U.S. may be pursuing research that is outlawed by the BWC.

The United States' first interest in any form of biological warfare came at the close of World War I. The only agent the U.S. tested was the toxin ricin, a product of the castor plant. The U.S. conducted tests concerning two methods of ricin dissemination: the first, which involved adhering the toxin to shrapnel for delivery by artillery shell, was successful; the second, delivering an aerosol cloud of ricin, was proven less successful in these tests. Neither delivery method was perfected before the war in Europe ended.

...
Wikipedia