I'm not a snake expert (not even close) but that's a gray rat snake. Not poison but they get very large. As least thats what we call them around here. They do come in variations of color.
We have a lot of white oak, king, and black rat snakes here. The black snakes are always in the chicken pen. They are not large enough to eat the chickens I guess they're trying to get the eggs?
We have a few copperhead but very rarely do you see a rattler or a cottonmouth even though they are around.