United States vs Mississippi River

United States and Mississippi River both are nouns.

Word	Noun	Adjective	Verb	Adverb
United States	Yes	No	No	No
Mississippi River	Yes	No	No	No

United States (noun)	Mississippi River (noun)
the executive and legislative and judicial branches of the federal government of the United States	a major North American river and the chief river of the United States; rises in northern Minnesota and flows southward into the Gulf of Mexico
North American republic containing 50 states - 48 conterminous states in North America plus Alaska in northwest North America and the Hawaiian Islands in the Pacific Ocean; achieved independence in 1776