The Exell Helium Plant was the largest helium plant in the world, and the largest single source of refined helium for around 25 years. It was constructed in 1943, when demand for helium for blimps was at a peak, and operated until 1997, when it was closed by the Helium Privatization Act of 1996, requiring the government to give up its dominance of the helium market. The Exell plant was one of several helium plants built and operated by the Bureau of Mines, starting with the Amarillo Helium Plant in 1927. After WWII the plant provided helium mostly for military programs, including blimps that continued to be produced into the 1970s, as well as for nuclear weapons, intercontinental ballistic missiles, NASA space programs, and for a growing use of the material in laboratory and computer manufacturing. By the time the plant closed, it was operated by the BLM, which took over federal helium programs from the Bureau of Mines. The plant remains closed and unmaintained after being auctioned off in 2011.