Did you feel it? I know I did. Lisa woke me up as she felt it first. She thought I was having a seizure or something. When we both realized that it wasn't me and it wasn't the dog either (who mostly slept through it) we understood that it was an Earthquake. See usgs.gov - Magnitude 5.2 - ILLINOIS. We met Reese in the hallway as it woke her too, but by that point it was over. I've never felt an Earthquake in my life, so it was a pretty exciting experience. I'm glad that Reese was able to sense it as well as she's my little scientist. Olivia awoke moments later and neither of them were scared at all.
It's always hard to reference how powerful an earthquake might be in relative terms. Here's a good cheat sheet hosted by Michigan Tech: Earthquakes Magnitude Scale and Classes.
Update (10:14am): We just had an aftershock while I was at work. Take a look: usgs.gov - Magnitude 4.5 - ILLINOIS.