DNA testing has shown that Kiger mustangs are descended largely from Spanish horses brought to North America in the 17th century, a bloodline thought to have largely disappeared from mustang herds before the Kiger horse populations were discovered in 1977.

Compact and well-muscled in appearance, their coloration and phenotype make them some of the most desired by private buyers when horses are removed from the feral herds.

Kiger mustangs are most commonly dun in color, although the breed registry also allows bay, black and roan horses to be registered.

Their descendants crossed with horses who escaped from or were released by other European settlers, including draft breeds brought by farmers and wagoneers and lighter riding horses brought by the United States Cavalry.

By the early 1970s, it was assumed that due to crossbreeding, the original Spanish stock had been eliminated from feral herds.

During the roundup, it was noticed that among the horses collected from the area, there was a group with similar color and markings.

DNA testing by the University of Kentucky showed close relation to the Iberian horses brought to the Americas by the Spanish in the 17th century.

The Riddle Mountain HMA, 50 miles (80 km) southeast of Burns, covers 28,000 acres (110 km2) and contains between 33 and 56 horses.

After roundups, horses with the desired physical characteristics (including phenotype and coloration) are returned to the herds to maintain a high quality of breeding stock.

[12] Genetic testing has shown that Kiger mustang is a descendant of the Colonial Spanish Horse.

[3] Several organizations exist which inspect and register Kiger mustangs; each has its own standards for entry into the stud book.