Columbia subject headings:
Big Bend National Park (Tex.)--Antiquities.
Fortification--Texas--Big Bend National Park--History.
Harvard subject headings:
Big Bend National Park Region (Tex.)--Antiquities.
Chihuahua (Mexico : State)--Antiquities.
Excavations (Archaeology)--Mexico--Chihuahua (State)
Fortification--Mexico--Chihuahua (State)
Mexico--History--Spanish colony, 1540-1810.
Princeton subject headings:
Big Bend National Park (Tex.)--Antiquities.
Fortification--Texas--Big Bend National Park--History.