The American Mammoth Donkey, commonly known as the Mammoth Jack, American Mammoth or American Mammoth Jack is a landrace of North American donkey, descended from multiple breeds of donkey imported to the United States.
The American Mammoth Jackstock was developed beginning in the earliest days of the United States, and it has been an integral part of American agricultural history. George Washington was one of the leading agricultural innovators of his day. Among his many interests was the improvement of livestock, including the development of an American ass breed that could be used to produce strong work mules.
Washington, with Henry Clay and others, obtained by gift and purchase a small number of jacks and jennies of the finest European breeds in the late 1700s and early 1800s. Interest increased quickly; Washington was offering his jacks for stud service by 1788. The Catalonian ass from Spain was of primary interest to American breeders, but the Andalusian (from Spain), Maltese (from Malta), Poitou (from France), Majorcan (from Majorca), and Italian strains were also used. Breeders blended these strains together, selecting the offspring for size, soundness, and strength and thus creating the American Mammoth Jackstock breed.
The primary function of American Mammoth Jackstock has always been to produce draft mules. Today, mules are as likely to be used in recreation as in agricultural work. The market for riding mules is also increasing, but this trend may or may not benefit the American Mammoth Jackstock breed, because Large Standard donkeys, which are lighter boned and more refined, are often used to produce these riding mules.
The American Mammoth Jackstock is found in the United States, with a small population in Canada. Within the breed, very few of the historic-type black Mammoth Jacks remain, and conservation of these strains is a priority for the breed.