Stadtallendorf was given city rights in 1960; it had been known until then simply as Allendorf.

During World War II, Stadtallendorf was a secret munitions centre.
The armament firms WASAG (Westfälisch-Anhaltische Sprengstoff Actien-Gesellschaft, "Westphalian & Anhaltish Explosives A.G.") and DAG produced munitions and explosives in two separate large facilities located in the woods nearby.
At the time, it was one of the largest of all munitions production centres in Europe.
The Munition centre continued throughout the war without being detected by the Allies.
Labor was provided by both German and foreign forced laborers, including prisoners of war and concentration camp inmates, housed in about a dozen camps in the surrounding area.

The 6 square kilometre premises where the wartime arms works were built were said to be one of Germany's biggest contaminated former industrial sites, in parts with high concentrations of chemical contaminants on residential properties.
Since 1991, the premises have undergone a far-reaching cleanup; in March 2006, the job was officially declared done.
According to information from the Hesse Environment Ministry, the cleanup cost € 167 million.
154 tonnes of contaminants were dug out of the ground, 697 tonnes were dug out of a dump, and 3 tonnes of TNT – still capable of exploding – were unearthed.
Stadtallendorf was given city rights in 1960; it had been known until then simply as Allendorf.
During World War II, Stadtallendorf was a secret munitions centre. The armament firms WASAG (Westfälisch-Anhaltische Sprengstoff Actien-Gesellschaft, "Westphalian & Anhaltish Explosives A.G.") and DAG produced munitions and explosives in two separate large facilities located in the woods nearby. At the time, it was one of the largest of all munitions production centres in Europe. The Munition centre continued throughout the war without being detected by the Allies. Labor was provided by both German and foreign forced laborers, including prisoners of war and concentration camp inmates, housed in about a dozen camps in the surrounding area.
The 6 square kilometre premises where the wartime arms works were built were said to be one of Germany's biggest contaminated former industrial sites, in parts with high concentrations of chemical contaminants on residential properties. Since 1991, the premises have undergone a far-reaching cleanup; in March 2006, the job was officially declared done. According to information from the Hesse Environment Ministry, the cleanup cost € 167 million. 154 tonnes of contaminants were dug out of the ground, 697 tonnes were dug out of a dump, and 3 tonnes of TNT – still capable of exploding – were unearthed.
Stadtallendorf