When I was a kid, the south side Chicago style was available only at hot dog stands and included:
A Rosen's bakery poppyseed bun (lightly steamed)
A fat, kosher beef hotdog with a skin (for the bite) boiled with a clove of garlic in the water
Chopped onion
Yellow mustard (Ketchup was forbidden)
One or two sport peppers (small, whole)
A kosher dill pickle spear
and MAYBE that weird, green pickle relish. Just maybe.
In later years, the hotdog evolved with a new chain of stands called Bozo's Hotdogs (later named Boz's hot dogs for trademark reasons)
It included:
A poppyseed bun (lightly steamed)
An all beef Ballpark Dinner Frank (still a fatso hotdog- skinny hotdogs were laughed at)
chopped onion
Yellow mustard
Seeded, fresh plum tomato wedges
Seeded cucumber spear
sport peppers (if requested)
celery salt
That's how I now serve my hotdogs at home. ( I occasionally still put a half clove of garlic in the boiling water) I found that one can request (ahead) for poppyseed hotdog buns at Publix- they will make them!
Good eating, in my book.