Sure looks like the garter snakes I use to chase people with when I was younger. Most of the ones we had in central PA looked like that, only a few had very distinct marking like Rallispec's pic.
Now for snake stories. We were hiking one day on a dead end trail along a swamp. On the way back we came upon what looked like a black snake that was about 5 feet long laying across the trail. No way around, so I decided we would get him off the trail by just scaring him. BIG MISTAKE.. He bunched up in a side to side motion preparing to strike. Then he lifted his head at least a foot and a half off the ground. Quite intimidating. So I got a long branch and decided to lift him and move him off the trail. Well, this is when I got the real surprise. When he layed over the branch you could see the diamond shaped marks all the way down his back. It was a 5 foot long black rattler who didn't have a rattle. Needless to say, I moved him off the trail quickly and we double timed it back to the car.