Underneath it lies tons of hazardous waste produced by a chemical plant that once stood in its place.
Today, Weldon Spring draws thousands of curious visitors each year.
They were immediately evacuated.
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After the war the Army began selling off pieces of the land.
These pieces of property are today the Busch Memorial Conservation Area and the Weldon Spring Conservation Area.
A small patch of land about 2,000 acres - was retained by the United States Atomic Energy Commission.
It was there the Commission built a uranium ore processing plant in 1955.
The processing plant operated until 1966.
The Army later abandoned the plan without ever producing the chemical at Weldon Spring.
The site sat abandoned for more than 20 years, but still contained contaminated equipment and hazardous chemicals.
Waste lagoons were filled with thousands of gallons of water contaminated with radioactive wastes and heavy industrial metals.
The official name of this site is the Weldon Spring Site Remedial Action Project (WSSRAP).
Completed in 2001, the mountainous structure covers 45 acres and stores 1.5 million cubic yards of hazardous material.
Incidentally, the top of the Weldon Spring waste disposal cell is the highest point in St. Charles County.
