An HMA is the BLM designation for Herd Management Area. This picture is where Beautiful was born, Beaty's Butte, Oregon, home of the original Kiger Mustangs. Currently, it's over 400,000 acres with 100-250 horses roaming.
Kitty Lauman, whose series, From Wild to Willing, I recommend if you want to know how to gentle your horse, used two Beaty's Butte horses in the training series. She speaks highly of the intelligence of these horses, and one of them looks an awful lot like Beautiful.