Mount Saint Helens vs Mount St. Helens

Mount Saint Helens and Mount St. Helens both are nouns.

Word	Noun	Adjective	Verb	Adverb
Mount Saint Helens	Yes	No	No	No
Mount St. Helens	Yes	No	No	No

As nouns, Mount Saint Helens and Mount St. Helens are synonyms defined as:

Mount Saint Helens and Mount St. Helens: an active volcano in the Cascade Range in southwestern Washington; erupted violently in 1980 after 123 years of inactivity

Other synonyms of Mount Saint Helens include Mt. St. Helens.

Mount Saint Helens (noun)	Mount St. Helens (noun)
an active volcano in the Cascade Range in southwestern Washington; erupted violently in 1980 after 123 years of inactivity	an active volcano in the Cascade Range in southwestern Washington; erupted violently in 1980 after 123 years of inactivity