American elm is a small to medium-sized (to very large) tree, at maturity with spreading branches forming a broad-spreading, fan-shaped crown.
Leaves are alternate, simple, 4–6 inches long, 2–3 inches wide, broadest at or below the middle with coarse, sawtooth edges. Smaller teeth appear along the lower side of the larger teeth. Base is uneven. Upper surface dark green, shiny, mostly smooth to somewhat rough.
Bark is gray, in cross-section with alternating brown and white layers, grooves deep, ridges flattened with thin closely pressed scales.
Twigs are slender, reddish-brown turning ash gray with age, hairy at first, smooth later.
Flowers February–April, in drooping clusters, red to green, small, petals lacking, the flower stalks originating from the same point.
Fruits March–May, in drooping clusters on long stalks originating from the same point; fruit about ½ inch long, seed surrounded by a thin wing; wing broadest in the middle, notched at the tip, with a fringe of silvery hairs along the edge.