This is about the gold rush. What happened to those towns after the gold was removed from the area? (North America History) Plss help

What makes fort sill historically unique among other regional military installations? a. it is the site where seven major commanders of us military efforts were trained. b. it houses the largest explosive weapons factory in the united states. c. it specializes in training soldiers to preserve the cultural artifacts of nations invaded by the us military. d. it is the oldest functioning installation in oklahoma.