Reptiles are cold-blooded animals with tough, dry skin and horny scales. Most hatch from eggs, laid on land, which have a leathery outer covering. This cover protects the embryo from dehydration. Some of the most widespread living reptiles include turtles and snakes, which are abundant here at Antietam. They love hiding under rocks and in leaf litter in the wet or wooded areas. Some, however, can also be found out in open, grassy fields. During the 2000-2001 Reptiles and Amphibians survey at the battlefield, the following reptiles were documented:

Eastern Garter Snake

Eastern Milk Snake

Northern Ringneck Snake

Northern Water Snake

Queen Snake

Common Snapping Turtle

Eastern Box Turtle

Eastern Painted Turtle

Redbelly Turtle

No poisonous snakes were confirmed to be present on the battlefield; however, habitat is suitable for the Copperhead.