Tom,
When you told me that you had a corn snake on your recent hike in the Woodmansie vicinity, I thought that you were quite fortunate. I have photo documentation of a corn from near here that dates back a number of years. Now that I have seen your photo and read your ID-clinching words " It was black and white checkered underneath" I must concur with Dragoncjo that your snake is a coastal plain milksnake, not a corn snake. Still a good find and a fine photo! Let me suggest that you routinely try to take a photo of the underside next time. I don't think an active corn would allow you to do that without striking. Corns tend to have black tail stripes and black odd shaped polygons on their underside.
I've also asked my colleagues of Herpetological Associates, Inc., Matt McCort, Dave Schneider, and Bob Zappalorti to take a look at your photo. They concur with my identification.
Lost Town Hunter