This cute little snake is a baby black rat snake and is also called an Eastern Rat Snake: Scotophis alleghaniensis). It is harmless. Often people see the pattern on its back and confuse it with a copperhead snake and kill it on site. An adult black rat snake is black on its back and has a white chin.
I found this guy on my porch by my front door yesterday.
In Southern Maryland where I live, the copperhead is the only poisonous snake.
Rat snakes and other non-venomous snakes have round pupils while Copperheads have an elliptical pupil like a cat’s eye. It looks like a small vertical slit in the eye.
If you aren’t sure what kind of snake you are looking at; it’s best to keep your distance.
Here is a guide to Maryland herps: http://www.dnr.state.md.us/wildlife/Plants_Wildlife/herps/index.asp