river vs Niagara River

river and Niagara River both are nouns.

Word	Noun	Adjective	Verb	Adverb
river	Yes	No	No	No
Niagara River	Yes	No	No	No

river (noun)	Niagara River (noun)
a large natural stream of water (larger than a creek)	a river flowing from Lake Erie into Lake Ontario; forms boundary between Ontario and New York