The Boston Terrier is a breed of dog of the Terrier dog type, originating in the United States of America. Frequently, variations on the standard are seen depending on the ancestry of the individual dog. At various times, the Bulldog, American Pit Bull Terrier, English Mastiff, Staffordshire Bull Terrier, and French Bulldog-among other breeds-have been crossbred with Boston Terrier lines to minimize inbreeding in what is necessarily a small gene pool. source