southwestern United States vs Golden State

southwestern United States and Golden State both are nouns.

Word	Noun	Adjective	Verb	Adverb
southwestern United States	Yes	No	No	No
Golden State	Yes	No	No	No

southwestern United States (noun)	Golden State (noun)
the southwestern region of the United States generally including New Mexico, Arizona, Texas, California, and sometimes Utah and Colorado	a state in the western United States on the Pacific; the 3rd largest state; known for earthquakes