While digging tunnels in the 1930's, an untold number of mostly black, migrant workers contracted acute silicosis and died. The deaths were covered up and the bodies of the workers were place in unmarked graves without a proper burial. Family members were never notified of the deaths and had no idea what had happened to their loved ones. It wasn't until congressional hearings in the 1970's that the the bodies were uncovered and given a proper burial along with a memorial.
Check out the first part of our investigation of the site here: