Pueblo Depot Activity (PUDA), formerly known as the Pueblo Ordnance Depot and the Pueblo Army Depot, was a U.S. Army ammunition storage and supply facility. Responsibility for the depot fell upon the United States Army Ordnance Corps, and the first civilians were hired in 1942 as operations began. The mission quickly expanded to include general supplies as well. It is a 24,202-acre (97.94 km2) site located 14 miles (23 km) east of Pueblo, Colorado at 38°19′37.07″N 104°20′22.4″W. In 1945 they began to receive mass amounts of equipment returning from the combat theaters of World War II. Therefore, the mission expanded yet again to include the maintenance and refurbishing of artillery, fire control, and optical material. In 1951 the depot assumed responsibility to distribute U.S. Air Force ammunition for an eight-state area, as well as storage of strategic and critical materials for the General Services Administration (GSA). They were also tasked to rebuild and provide on-site maintenance support for guided missiles, ensure calibration and maintenance of electronic test equipment and radio-controlled aerial targets. They would also provide specialized training for new Army equipment as needed. In 1952, Rocky Mountain Arsenal in Denver, Colorado transferred chemical agents and chemical munitions to Pueblo Army Depot for secure storage. In 1974 Pueblo Army Depot was redesignated as Pueblo Depot Activity.

A chemical weapon (CW) is a specialized munition that uses chemicals formulated to inflict death or harm on humans. According to the Organisation for the Prohibition of Chemical Weapons (OPCW), this can be any chemical compound intended as a weapon "or its precursor that can cause death, injury, temporary incapacitation or sensory irritation through its chemical action. Munitions or other delivery devices designed to deliver chemical weapons, whether filled or unfilled, are also considered weapons themselves."