The Staffordshire Bull Terrier, commonly called the Staffy or Stafford, is a shorthaired, purebred dog breed of medium size that originated in the Black Country of Staffordshire in the English Midlands. Their earliest beginnings date back centuries when the Mastiff and Bulldog were closely linked, and were used for bull and bear baiting which required large dogs in the 100–120 lb range. After Parliament passed the Cruelty to Animals Act 1835, dog fighting became a clandestine sport. Breeders migrated away from the heavier bulldogs, and introduced terrier blood into their crosses for gameness and agility. The ancestral crosses of bulldogs and terriers were known by different aliases, such as the Patched Fighting Terrier, Staffordshire Pit-dog, Brindle Bull, and Bull-and-Terrier, which can be confusing relative to the modern Staffordshire Bull Terrier's brief history. Those same crosses were also called half-and-halfs and half-breds but were more commonly known as the bull and terrier, which was not a breed but the beginning of several breeds.Individual types and styles of dogs that were crossed varied by geographic region. For example, the progeny from one area may have a higher percentage of terrier than bulldog, whereas other reports claim that bulldog to terrier was preferred over bull and terrier to bull terrier. Dog breeders made careful selections in their breeding programs in order to produce inheritable traits from specific dog types. Many of the breed types that were used to create the early fighting dogs have long since become extinct, but certain genetic traits are represented in the new breeds that were developed over time.By the mid-1860s, James Hinks was developing a new breed which came to be known as the 'Bull Terrier'. Hinks' son, also named James, described the new breed as "the old fighting dog civilized, with all of his rough edges smoothed down without being softened; alert, active, plucky, muscular, and a real gentleman”. Another group of breeders preferred the fighting bulldog–terrier crosses over the Hinks’ outcrosses, and two different breeds of Bull Terriers emerged: the Hink's Bull Terrier or White Cavalier, and the Staffordshire Bull Terrier. An article published in the Proceedings of the National Academy of Sciences of the United States of America (PNAS) states that the early history of the Staffordshire Bull Terrier "is identical to the Bull Terrier which was a cross between a Bulldog and a Black and Tan Terrier". It describes the breed as the result of deliberately crossing "a Bull Terrier (itself a mix of a Bulldog and a Black and Tan Terrier) and a smaller terrier (possibly a Manchester Terrier or a White Terrier)."
It was sometime during 1932 and 1933 that dog breeder Joe Dunn from Quarry Bank worked toward getting the Black Country breeders' strain of bull terriers recognised as purebreds by The Kennel Club. In early 1935, Dunn obtained permission from TKC to hold a variety dog show to gage the level of interest in showing Staffords, and offered cash to attract owners. The show was held in April 1935, and was a success. After the show, Dunn decided to form a club, and invited other dog breeders to the meeting. Those in attendance agreed to name their club "The Staffordshire Bull Terrier Club". It was subsequently accepted by The Kennel Club (TKC) in July 1935, marking an official milestone for the Staffordshire Bull Terrier's acceptance into TKC's breed registry. It wasn't until 1974 that the American Kennel Club (AKC) admitted the Staffordshire Bull Terrier as their 121st registered breed.