One-Million-Liter Test Sphere

The One-Million-Liter Test Sphere, located at Fort Detrick, Maryland, is a historic biological warfare testing facility known for being the largest aerobiology chamber ever built. Constructed between 1947 and 1948, it was used by the U.S. Army from 1951 to 1969 to study infectious aerosols and test biological munitions. The impressive four-story, 131-ton stainless steel structure was designed to safely contain biological experiments, including tests involving live animals and human volunteers. Although it ceased operations in 1969 following the disestablishment of the U.S. offensive biological warfare program, the chamber was recognized for its historical significance and added to the National Register of Historic Places in 1977. Today, it stands as a unique site for researchers and tourists interested in the history of biological warfare and aerobiology.