* Nevada
* California
* Utah
* Oregon
* Arizona
* Wyoming
* Colorado
* New Mexico
These areas encompass the Great Basin and other western regions, where the horses were able to roam freely and establish large herds.
It is important to note that mustangs are wild horses, meaning they are not domesticated and live in the wild. While they are most abundant in the western US, they can be found in other areas as well, often as a result of feral populations established from escaped or abandoned horses.