Baja California Peninsula vs Lower California

Baja California Peninsula and Lower California both are nouns.

Word	Noun	Adjective	Verb	Adverb
Baja California Peninsula	Yes	No	No	No
Lower California	Yes	No	No	No

As nouns, Baja California Peninsula and Lower California are synonyms defined as:

Baja California Peninsula and Lower California: a mountainous peninsula on northwest Mexico

Other synonyms of Baja California Peninsula include Baja California.

Baja California Peninsula (noun)	Lower California (noun)
a mountainous peninsula on northwest Mexico	a mountainous peninsula on northwest Mexico