Woodchucks and groundhogs are the same thing, but 'woodchuck''s origins date back to a Native American name for the animal, "wuchak". Thus, I consider it a more correct term than "groundhog", which came second.

Woodchucks, Marmota monax, are a type of marmot, which in turn is a type of ground squirrel. Yes, they're squirrels (so are prairie dogs and chipmunks). This guy was seen in Maryland. They're EVERYWHERE on base.

This photo is also featured in the Encyclopedia of Life:

eol.org/pages/327979