I am doing a presentation on the evolution of American weapons of war, my part is to do weapons from WW1 & WW2. I was trying to find out if america used chemical weapons in WW1 but couldn't find any information on it. Although I did find that during WW1 chemical weapons such as tear gas, mustard gas, phosgene, and chlorine gas were used, but I'm not sure if America used these or not.
The US produced chemical weapons during WW1, but never deployed them to the battlefield. They started large scale production of a new agent - Lewisite planed to be used by 1919.They did send chemical weapons to Europe in WWII, but didn't use them. There was an incident during WWII where a sinking of a US ship caused a spill of mustard gas at the port of Bari in Italy. The US disposed of all chemical and biological weapons by 1970.
Related to this, my undergraduate campus, American University, was actually used during World War I as a chemical warfare lab/testing grounds. To this day the Army Corps of Engineers is still having to excavate the homes around campus because they are finding unexploded shells full of mustard gas. These are homes worth millions of dollars and owners are very much not happy about this. In the 1990s, the whole turf field was dug up and replaced with new dirt, along with the area around the day care center, as they found incredibly high arsenic levels in the earth around that area.
So while I'm not an expert on if/how they were used in battle, they were absolutely working on them and had very little regard for how to properly dispose of the results.
If you are curious about the development of Lewisite, or the US production of mustard gas during the war, I wrote up a blog post on this a little while back: Conant's war: Inside the Mouse-trap.
The US intended to use chemical weapons in the war but they didn't get them together in time. They didn't even have a chemical warfare corps by the time they entered the war; they hadn't manufactured even gas masks or trained soldiers how to deal with them. One of the heads of the US chemical effort went on to play a key role in the development of the atomic bomb.