Columbia subject headings:
Fortification--Puerto Rico--San Juan--History.
Puerto Rico--History--To 1898.
San Juan (P.R.)--Buildings, structures, etc.
San Juan National Historic Site (San Juan, P.R.)
Harvard subject headings:
Fortification--Puerto Rico--San Juan--History.
Puerto Rico--History--To 1898.
San Juan National Historic Site (San Juan, P.R.)
San Ruan (P..R)--Buildings, structures, etc.
Princeton subject headings:
Fortification--Puerto Rico--San Juan--History.
Puerto Rico--History--To 1898.
San Juan (P.R.)--Buildings, structures, etc.
San Juan National Historic Site (San Juan, P.R.)