I've been to almost every bar/grill in Chicago (I promise, i don't have a drinking problem) and Illinois Bar has the best burgers hands down! The burgers are amazing, I've walked in early in the afternoon and the cooks were preparing the patties in the kitchen, you could taste the quality and freshness of the burger. The buns are toasted and specially made for the size of these burgers. Get the works! Grilled onions, bacon, cheddar cheese, lettuce and tomatoes. If you are not ready for a huge portion get the baby burgers. The fries are also delicious and homemade. They have a coin operated pool table in the backroom along with LCD TVs. The Beer selection is average, I'm partial to the Belgium's brews. The crowd is for the most part regulars but very friendly.
My only complaint is the entertainment aspect of the backroom. I wish the owner would invest in a projector and surround sound system. At the very least the old CRT television sets are gone.