4. Into the sea: From 1967 to 1970, the U.S. Army disposed of thousands of chemical warfare agents and ammunition into the sea as part of Operation Cut Holes and Sink 'Em (CHASE).
5. No more: Congress passed a law in 1972 known as the Marine Protection, Research and Sanctuaries Act prohibiting this kind of dumping.
6. Date of destruction: In 1997, the United States ratified the Chemical Weapons Convention Treaty and agreed to destroy all of its chemical weapons by April 29, 2012.
7. Work not done: 90% of the U.S. stockpile -- 30,500 tons -- was destroyed by the treaty date in 2012 at depots in Alabama, Arkansas, Indiana, Maryland, Oregon, Utah and Johnson Atoll in the Pacific. The remaining 10% -- close to 3,100 tons -- is at two sites in Colorado and Kentucky.
9. Don't burn it: Residents in Colorado and Kentucky protested the use of incineration to get rid of the chemical weapons stockpile. The process of neutralization was adopted.
8. Pueblo's stockpile: The Pueblo Chemical Depot has about 780,000 shells containing mustard agent.
9. The last one: The Blue Grass Army Depot in Richmond, Kentucky, will have the remaining chemical agent stockpile, which is a fifth of the size of the one at Pueblo Chemical Depot. But the Kentucky site has a larger variety of chemical weapons, including nerve agent.