Home Postcodes by state SA 5221 Postcode 5221 5221 is the postcode for 3 localities in SA: American River, Ballast Head and Muston. Localities with postcode 5221American RiverSABallast HeadSAMustonSA Postcode 5221 State or territory South Australia (SA) Localities 3 Council area Kangaroo Island Council area based on Australian Bureau of Statistics data (ASGS Edition 3), CC BY 4.0. Postcode 5220 · Postcode 5222