Taken from the World Trade Center Register, this is a list of WTC tenants that worked in the areas of engineering and construction.
America Bureau of Shipping (Floor 91 North Tower)
EQE International (Floor 52 North Tower)
Gibbs & Hill (Floor 91 South Tower)
John J. McMullen Assoc. Inc. (Floor 15 South Tower)
Mancini Duffy (Floors 15 and 22 South Tower)
Raytheon Engineers & Construction (Floor 93 North Tower)
Washington Group Intl. (Floor 91 South Tower)
Deerpath Construction of New York (South Tower)
IBN Group (North Tower)
Regional Alliance Small Contractors (Floor 38 North Tower)
Turner Construction Co. (Floor 38 North Tower)
Photo courtesy of the Federal Emergency Management Agency (FEMA), Washington, D.C.