Why is there no Western Seaboard? Or Gulf Seaboard?

Well, OK, but that article even notes that it’s pretty obscure:

Bolding mine. And given its location, it’s actually the east side of the south side.

Milwaukee’s East Side is a neighborhood right up against the lake and I lived there for 5 years while a student. As an otherwise lifelong Chicagoan, it always seemed strange to say/hear East Side.