I just heard back from the snake expert. He has identified my little visitor as a young Northern Black Racer. I was surprised, as his coloring and markings are not at all what I thought would be a Black Racer. However, upon further investigation of my own, I did find that they are highly patterned and colored as this one is, when they are still young. Also, we did have an adult Black Racer visit our front sidewalk probably a year or more ago! So, it fits! Any way, he / she is not poisonous and will help keep our rodent and insect population under control!