July 1 or 2, 1806, at Traveler's Rest, Montana.

The tallest native cottonwood, with open crown of erect branches and sticky, resinous buds with balsam odor. Leaves 3-6 in (7.5-15 cm) long, 2-4 in (5-10 cm) wide. Height: 60-120 ft (18-37 m). Diameter: 1-3 ft (0.3-0.9 m), sometimes much larger.

Moist to wet soils of valleys, mainly on stream banks and flood plains, also on upland slopes; often in pure stands and with willows and red alder.

Southern Alaska south to southern California and east in mountains to extreme southwestern Alberta and Montana; also local in southwestern North Dakota and northern Baja California.