These are all tentants of the buildings, and provide a potentially very interesting glimpse in to what, a hellbent governement would want to either,
control over or just eliminate.
en.wikipedia.org...
Bureau of Alcohol, Tobacco, Firearms and Explosives
U.S. Secret Service
Securities & Exchange Commission
Airport Access Program
Access to the Region's Core (ARC)
This is where American Airlines 11 impacted: Marsh USA
Here' some more
New York Society of Security Analysts,
Foreign Credit Insurance Association
And of course tons of trading and banking going on! Quite an interesting read through, about the tenants who occupied WTC 1 through 7.