The Chicago-style dog features an all-beef frankfurter adorned with celery salt, relish, sport peppers, a pickle, tomato slices, onions, and yellow mustard on a poppy seed bun.

However, the one condiment Chicago natives adamantly reject on this topping-rich hot dog is ketchup, and several theories attempt to explain the city’s collective aversion to it.

It could be because Chicago was the meat-packing capital of the U.S. in the early 20th century, and hot dogs, among other meat products, are still taken very seriously in the city.

Due to the belief that ketchup can overpower the taste of a high-quality sausage or mask the flavor of an inferior or spoiled dog, Chicago natives prefer to skip it.

Alternatively, Chicago natives might not want their signature hot dog style to stand against the taste of ketchup and would rather have their uniquely flavored dog stand out.