Mason and Dixon's line vs Mason and Dixon line

Mason and Dixon's line and Mason and Dixon line both are nouns.

Word	Noun	Adjective	Verb	Adverb
Mason and Dixon's line	Yes	No	No	No
Mason and Dixon line	Yes	No	No	No

As nouns, Mason and Dixon's line and Mason and Dixon line are synonyms defined as:

Mason and Dixon's line and Mason and Dixon line: the boundary between Maryland and Pennsylvania; symbolic dividing line between North and South before the American Civil War

Other synonyms of Mason and Dixon's line include Mason-Dixon line.

Mason and Dixon's line (noun)	Mason and Dixon line (noun)
the boundary between Maryland and Pennsylvania; symbolic dividing line between North and South before the American Civil War	the boundary between Maryland and Pennsylvania; symbolic dividing line between North and South before the American Civil War