The Staffordshire Bull Terrier, also called the Staffy or Stafford, is a purebred dog of small to medium size in the terrier group that originated in the northern parts of Birmingham and in the Black Country of Staffordshire, for which it is named. They descended from 19th-century bull terriers that were developed by crossing bulldogs with various terriers to create a generic type of dog generally known as bull and terriers. Staffords share the same ancestry with the modern Bull Terrier, although the two breeds developed along independent lines, and do not resemble each other. Modern Staffords more closely resemble the old type of bull terrier, and were first recognised as a purebred dog breed by The Kennel Club of Great Britain in 1935.
Within the broad sweep of dog history, the story behind the modern Stafford is rather brief and somewhat confusing because of the multiple aliases attached to these dogs in centuries past, such as the "Patched Fighting Terrier", "Staffordshire Pit-dog", "Brindle Bull", and "Bull-and-Terrier". Similar crosses also had aliases such as half-and-halfs and half-breds. Blood sports such as bull-baiting and bear-baiting were outlawed with the passing of the Cruelty to Animals Act 1835 by Parliament, making it illegal to bait animals but promoting the matching of dogs against each other. Dog breeders migrated away from the heavier bulldogs, and introduced terrier blood into their crosses for gameness and agility. These bull and terrier crosses produced the ancestral breeding stock that, over the course of decades, evolved into the modern conformation show dogs we know today as the Staffordshire Bull Terrier and the Bull Terrier. It was shortly before the American Civil War that immigrants from Great Britain brought their bull and terrier crossbreeds into the U.S. They became the ancestral progenitors of the American Staffordshire Terrier (AmStaff), Miniature Bull Terrier, Boston Terrier, and American Pit Bull Terrier.
By mid–19th century, and with stricter enforcement of the 1835 Cruelty law, conformation dog shows became the new focus for dog breeders across Great Britain. As a result, reputable breeders no longer needed to breed dogs with attributes necessary for bull, bear and rat-baiting, so dog breeders focused on conformation and temperament to produce dog show champions. The growing popularity of dog shows created the need to document and preserve dog show results, establish rules for showing, and document pedigrees of the developing new breeds to prevent fraud. To serve that purpose, the Kennel Club was founded on April 4, 1873. They established dog show rules, but were not involved in establishing the breed standards by which each breed of dog would be judged. Local dog clubs were responsible for creating the breed standard for their particular breed of dog.