You can also get a "chicago dog" which is a hot dog with tomatoes and pickles and some other shit on it, if you're interested. Portillo's is a long running place that offers those and "chicago style vienna beef" sandwhiches
Don't go to Portillo's. Go to any of the many small ma and pop hot dog stands. Portillo's is very mediocre at everything they do. Not bad, but there's always a local option that does it better in Chicago.
If you want a hot dog go to Wiener Circle on Clark street, but only if you go after midnight. Don't go there during sober hours. After midnight the place becomes a show in itself. If you do go, here are a couple tips. NO matter how packed it is, the louder and more obnoxious you are the quicker you will get served. You can honestly cut the entire line if you walk in screaming and calling the people behind the counter mother ****ers. Tip #2: order the chocolate shake, you won't be disappointed. Here is a clue...they don't sell shakes there.