It's on the border of being in the South Loop, on Harrison, west of Dearborn. Great, kind of funky brunch food. They have excellant pancake flights - four different kinds of silver dollar pancakes based on a common theme (like chocolate or wine), as well as interesting omelettes.
Though not River North, you might want to consider Brett's. A wonderful, warm and cozy spot, serves an excellent brunch. I haven't been there lately, but my memories of brunch there are wonderful and I wouldn't hesitate to return. It's not terribly large, though certainly large enough and not packed.
(I think she just changed the name, actually, to Brett's Cafe Americain--like Casablanca)
2001 W. Roscoe