Moreau River vs river

Moreau River and river both are nouns.

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

Moreau River (noun)	river (noun)
a river that rises in western South Dakota and flows eastward to the Missouri River	a large natural stream of water (larger than a creek)