Two years after the 1995 Oklahoma City bombing , a little over $ 1 million was granted to institute a counterterrorism program . Park officials were trained to note the activity of tourists , and inconspicuous electronic detection devices were installed . After the September 11 attacks in 2001 , security efforts were more prominent , security checkpoints moved to the entrance of the visitor center . At the checkpoints , visitors are screened by magnetometers and x-ray equipment , devices which have been in place since 1997
September 11 attacks
September 11 attacks
Gateway Arch