This is one of the major trees in the eastern deciduous forests of the United States (along with sugar maple, American beech and formerly American chestnut). It is a tall, pyramid-shaped tree with slender and sometimes drooping branches. It is more likely to have a rounded than a pointed crown. The twigs and branches are more flexible than those of spruces or firs and tend to "ride with the wind". It can grow to a height of 140 feet, but in forest environments is often smaller. Its native range is around the Great Lakes, New England, Northern Atlantic Coast and south to Alabama in the mountains.

The needle leaves are flat - ½ to 1 inch long and 1⁄16 inch wide. These needles have pointed bases with short stalks and grow in two rows. When the needles drop, the bases remain attached to the twigs making them rough. This distinguishes them from the firs that have smooth twigs. They are dark green above and light green below with two silvery stripes. The pollen cones are light yellow while the female or seed cones are pinkish-green and mature to brown with a total length of only ½ to 1 inch long. The seeds have wings twice as long as the seed.

The hemlock is sometimes used as an ornamental and can be trimmed to shape. It is also a source of lumber and pitch, though the wood is tough and knotty. The bark is used for tanning. It makes a poor Christmas tree because the leaves quickly dry up and fall off after it is cut. It is also called the Canadian hemlock. The similar Carolina hemlock is found in the southern mountains from Virginia to Georgia. It is the state tree of Pennsylvania.

An invasive insect called the hemlock woolly adelgid is killing trees from the Carolinas to Maine and is threatening the species. These aphid-like insects are hard to see but leave white wooly masses on the underside of hemlock twigs. Scientists are working on a fungus treatment that may control the insect and some states have released insect predators to help control the adelgid.