What three mountain systems are in the US?

The three major mountain systems in the United States are the Rocky Mountains, the Appalachian Mountains, and the Sierra Nevada. The Rocky Mountains extend from Canada down to New Mexico, known for their rugged terrain and diverse ecosystems. The Appalachian Mountains run from Canada through the eastern United States to Alabama, characterized by rolling hills and rich biodiversity. The Sierra Nevada, located primarily in California, is noted for its stunning granite peaks and national parks, including Yosemite.