The U.S. Army Corps of Engineers built a total of 72 Atlas "F" Missile Bases in the early 1960's. Each base cost an average of $15 Million in 1960 dollars. The cost estimates to build this structure in 2008 dollars range as high as $60 Million. There are more than 600 Tons of structural rebar steel in each site and the epoxy-hardened concrete walls range in thickness between 2.5 to 9.0 feet. The bottom of the silo structure is nearly 200 feet below the surface. Even today, these structures are considered "one of the strongest structures built by man".

These images show how these missile bases were built, but they don't convey the feeling of massiveness that you get when you see this in person. Let's just say "They don't build'em like this any more" !