Columbia subject headings:
Bridges--New York (State)--Exhibitions.
Bridges--Niagara River (N.Y. and Ont.)--Exhibitions.
Bridges--Ontario--Exhibitions.
Harvard subject headings:
Bridges--Exhibitions.
Bridges--New York (State)--Exhibitions.
Bridges--Niagara River (N.Y. and Ont.)--Exhibitions.
Bridges--Ontario--Exhibitions.
Niagara Falls (N.Y.)--Buildings, structures, etc.
Princeton subject headings:
Bridges--New York (State)--Exhibitions.
Bridges--Ontario--Exhibitions.
Niagara River (N.Y. and Ont.)--Bridges--Exhibitions.