Soon after the United States entered the First World War in 1917, the American University's offer of its campus and buildings for war work was accepted.
The permanent buildings and part of campus were turned over to the Bureau of Mines on July 6, 1917, for use as chemical warfare laboratories and proving grounds. McKinley Hall served as one of the first of these laboratories.
On August 30, 1917, the Thirtieth Engineers, later known as the first gas regiment, was organized here. Companies A and B and First Battalion Headquarters marched out of the American University on Christmas Day, 1917 and sailed for France the next day. They were soon followed by Companies C and D, and later by Companies E and F which were organized at Fort Myer.
In June 1918, the chemical warfare organization of the Bureau of Mines was transferred to the War Department as a step toward the creation of the chemical warfare service, now the U.S. Army Chemical Corps.
Dedicated in 1960 by Veterans of the First Gas Regiment.