Adults can become quite large and are known to reach up to eight feet, being the largest snake found in Canada. The record length is 101 inches (2.6 m), making it (officially) the longest snake in North America. Unofficially, indigo snakes (Drymarchon couperi) are known to exceed them, and one wild-caught pine snake (Pituophis melanoleucus), with a portion of its tail missing, measured 111 inches (2.8 m).
Juveniles are strongly patterned with brown blotches on a gray background (like miniature fox snakes). Darkening occurs rapidly as they grow. Adults are glossy black above with white lips, chin, and throat. Sometimes traces of the "obsolete" juvenile pattern are still discernible in the skin between the scales, especially when stretched after a heavy meal.
Other common names include: Alleghany black snake, black chicken snake, black coluber, black pilot snake, chicken snake, mountain black snake, mountain pilot snake, pilot, rat snake, rusty black snake, scaly black snake, cow snake, schwartze Schlange, sleepy John, and white-throated racer.
