Where are you staying in chicago? For deep dish in chicago(which native Chicagoans rarely eat btw) downtown I would go with pizzeria due, not uno but make sure due. For thin crust chicago style I love pizanos pizza on Madison. The best hot dog in chicago is at hot Doug’s, but that’s a little away from city center so portillos is still good and their service at busy times is a thing to behold, also get the cake shake. For more upscale experience osteria nico is amazing, and green street BBQ has the best brisket and pork ribs ever, just skip the sides. I work at the chicago board of trade if you want to come see the trading pits in action just pm me, I’ll take you for a beer downstairs afterwards. My trading hours are 9-1.
Enjoy, it’s a great city.