Why is this built and when and for which use?

At 6,100,000± square feet, SubTropolis is the world's largest underground business complex. Mining started in the 1940s and in 1964 Ford, Pillsbury and Russell Stover became our first tenants. SubTropolis is now home to more than 55 international, national, regional and local companies with more than 2,000 employees working here everyday. For more information, please visit: https://huntmidwest.com/industrial-space-for-lease/what-is-subtropolis/

Actually SubTropolis was built from mining limestone from the Randolph mine. That began in the 30's or 40's. Subtropolis was opened in the mid 60's. This is a climate controlled environment and is available for businesses that need warehouse space and offices can be built to suit. They also in recent years have offered SubTropolis Storage for RV's & Boats storage. Currently there is over 55 Million square feet of leasable office/warehouse. It's absolutely fascinating to drive through, and even trains load and unload inside.

There are businesses there. There is a race held there annually in February as well (5K). It isn't really places for shopping. More industrial or warehouse type business.

Well there are like 50 different company buildings in there. Some of them are for Ford.