river vs Little Sioux River

river and Little Sioux River both are nouns.

Word	Noun	Adjective	Verb	Adverb
river	Yes	No	No	No
Little Sioux River	Yes	No	No	No

river (noun)	Little Sioux River (noun)
a large natural stream of water (larger than a creek)	a river that rises in southwestern Minnesota and flows southwestward to the Missouri River in western Iowa