The ecoregion covers an area of 34,630 sq miles (89,691 km2) encompassing the Piedmont and coastal plain of seven states, extending from coastal southwestern Maine, southeastern New Hampshire, eastern Massachusetts, and Rhode Island, southward through Connecticut, New York State, New Jersey, southeast Pennsylvania, Delaware and Maryland.

They cover large areas at low and middle elevations, typically on flat to gently rolling terrain.

), red maple (Acer rubrum), sugar maple (Acer saccharum), white ash (Fraxinus americana), tulip tree (Liriodendron tulipifera), American beech (Fagus grandifolia), black cherry (Prunus serotina), black birch (Betula lenta), black tupelo (Nyssa sylvatica), and American elm (Ulmus americana).

In sandier or more acidic soils are mountain laurel (Kalmia latifolia), blueberry (Vaccinium pallidum), huckleberry (Gaylussacia baccata), and swamp azalea (Rhododendron viscosum).

[2] Hemlock-northern hardwood forests occur in deep coves, moist flats, and ravines.

These trees often form a deciduous canopy, but are sometimes mixed with hemlock (Tsuga canadensis) or white pine (Pinus strobus).

Shrubs such as hillside blueberry (Vaccinium pallidum), black huckleberry (Gaylussacia baccata), and mountain laurel (Kalmia latifolia) are common in the understory and can form a dense layer.

Red maple is a common tree, and can be found with swamp tupelo, white ash, American elm, pin oak (Quercus palustris), swamp white oak (Quercus bicolor), and silver maple (Acer saccharinum).

[2] Some of the animals that live in the Northeastern coastal deciduous forests are white-tailed deer, eastern gray squirrels, chipmunks, red foxes, sparrows, chickadees, copperheads, rattlesnakes, northern water snakes, box turtles, snapping turtles, black rat snakes, garter snakes, snails, American toads, coyotes, black bears, bobcats, beavers, woodchucks, skunks, and raccoons.

[7] Other fauna that occupy the area include bog turtles, ducks, rabbits, eagles, and (formerly) Canada lynx and sea mink.