How do you spell Sumpter

Available Definitions:
1)  n. - The driver of a pack horse.
2)  n. - A pack; a burden.
3)  n. - An animal, especially a horse, that carries packs or burdens; a baggage horse.
4)  a. - Carrying pack or burdens on the back; as, a sumpter horse; a sumpter mule.