In the near north Chicago suburbs it's all WSCR day and night. Their ground wave signal is excellent as others have pointed out. It's listenable in St Louis during the day and just east of the Twin Cities. At night it's another story. If you're anywhere in the southeast Cuba gives it a very rough time. I spent a few days in eastern Ohio a few years ago and at night there Cuba sometimes interfered.
Retro/other: Back in the early 60s then WMAQ could be heard at night all over the US and Canada. If I remember correctly 670 was the first of the Chicago clears to be broken down when KBOI moved over in the mid 60s. Now if you're on the west coast there are plenty of stations on 670 in Las Vegas, Simi Valley, and Idaho. Maybe more.
Here in Central Ohio Cuba has interfered with WSCR for decades. It's not nearly as bad as it used to be. I can remember many nights in the 90s when Cuba was so strong here that then-WMAQ was nowhere to be found no matter how you turned your radio. As close as northern and northwest Ohio, it was a different story.
It was mentioned earlier that WSCR can be heard faintly around Columbus and that is indeed the case. I've heard it 30 miles east of town out around Buckeye Lake, but only on really cold winter days. That's the farthest I've heard their groundwave.