I found this guy yesterday crossing the corner of my backyard. I got a few pics and then let him go on his way. It's a male Wood Turtle (Glyptemys insculpta). Unfortunately they're not as common around here as they once were.
Nice Seth. You should have kept him and found a female and start breeding them so they are more common in your area. Would he get along with your box turtles?
They're considered a threatened species in my state and we're not allowed to keep them. But I did patch up a few that were hit by cars in the past and I kept them briefly.
They get along with box turtles pretty well but these guys are much more aquatic and spend a good part of the year in water.