Black walnut (Juglans nigra) is one of the most prized and valuable of North American hardwoods. It is also called eastern black walnut and American walnut. Black walnut is found throughout the eastern U.S. A medium to large tree that typically grows 70 to 90 feet tall and two to three feet in diameter but can grow up to 150 feet tall and up to seven feet in diameter on really good sites. It is a relatively fast-growing tree that reaches maturity by 150 years but can live up to 250 years.