The state tree of Pennsylvania is the Eastern Hemlock, Tsuga canadensis, and has been since a decision by the state in 1931. It is an evergreen conifer found all over the state, but more often in the mountainous areas because it tends to prefer cooler, shady climates, and moist, well drained soil. The trees are capable of growing to more than 100 feet tall, and living for up to approximately 800 years; they are relatively slow-growing trees. Unfortunately, the hemlock woolly adelgid -- an insect from Asia -- was introduced as an invasive species into the United States in the 1920s, and feeds on the hemlock, leading to the destruction of many trees all over North America. After being infested, trees typically cannot live for more than a few years.
There were a number of reasons that the Eastern Hemlock was selected as the state tree of Pennsylvania, one of them being because the tree is so prolific throughout the state, and because it contributes to the beautiful scenic views all year round, even after the deciduous trees lose their leaves. The hemlock was also called the most "picturesque and beautiful" of all evergreen trees by A.J. Downing in the early 1900s as well. Prior to the hemlock becoming the state tree of Pennsylvania, it was one of the trees most frequently used by early settlers.
The lumber produced by the Eastern Hemlock is sturdy, and lasts for a number of years, making it a good choice for building homes. The bark of the tree was also used as the primary source of tannin, an acidic compound used in making leather. Pennsylvania's forests were nearly stripped entirely of the hemlock tree in the late 19th and early 20th centuries because of the tanning practice; fortunately, later conservation efforts helped to restore the trees to this area. It was partly due to these conservation efforts and improved forest management practices that the Eastern Hemlock would go on to become the state tree of Pennsylvania. Today, the trees may be used to make some paper products.
It is important to recognize that the Eastern Hemlock is not just the state tree of Pennsylvania, but is an important component of the ecosystem and provides habitat and food for a number of different animals as well. White-tailed deer, rabbits, squirrels, and other rodents all feed on the hemlock, especially in the winter when other sources of food become more scarce. It also provides habitat for certain birds.