Yep. Gray Rat Snake to be more specific. Since you took pictures and (apparantly) didn't kill it, I assume you knew that it was a harmless species. He/she'll be good to have around to keep the mice numbers down.
When I was a kid, I reached into a many hen nests feeling for eggs and grabbed a rat snake. Many of the old timers call them "chicken snakes" due to their habit of eating eggs and chicks. I kept a Corn Snake as a pet for a while. They're closely related with similar patterns, but different color. The Corn Snake has rusty orange/brown markings as opposed to the gray/black of the Gray Rat Snake.
Nice pictures, by the way.
BR