Looks like a black racer to me but it is a dark pic.
Jill

Considering his length, he looks too thin to be a cottonmouth, copperhead or any kind of rattler. The first picture shows some markings so I'm guessing he may be a common water snake.

If you will send your photos to this Professor Whit Gibbons at the University of Georgia, he might can ID it for you. He's ID'd a couple for me. He usually responds very quickly.
Here's his email addy:

gibbons@srel.edu

Jan

It's a Rat Snake. It looks like an intergrade between a Gray Rat Snake and a Black Rat Snake. Alabama has the Gray Rat Snake, the Black Rat Snake, and a large crossover population where the gene pools intergrade. This looks like a snake from an intergrade population.

Rat Snakes are very large and harmless snakes.

Thanks guys!! I knew I could count on ya'll to help. I emailed Whit Gibbons and he wrote me back promptly to tell me the same thing Wayne said- it was a gray rat snake.

Friendly snake - keep up the good work eating all those rats, Mr. Snake!