I apologize for missing replies here. Not even sure how I missed them on this one and only thread, as I've been getting replies to other threads. So I apologize. I only found the replies because I wanted to update about this NOT being a Box Turtle. 
After lots of reading and comparing pictures, the turtle has been identified as a Cumberland Slider. It's doing well so far and we're enjoying interacting with it. I've been trying to learn as much as possible now that we've identified the type and the specific requirements. I will try to get some pictures soon and post them. We've named it "Tilly" but I'm not sure about the sex, so we'll have to wait and see if the name stands.