The history of the American Pit Bull Terrier varies depending on what source you choose to cite. Some believe that it dates back to the time of the Roman's and the Molossian family of Dog. The Molossus as it was commonly called is believed to be the direct relative of today's Mastiff breeds of dogs.

Most sources seem to agree that the Pit bull can trace its relatives to the English and Scottish Bull dog types used in the sport of Bull Baiting. Bull Baiting became a popular sport in England during the 15th and 16th century. Bull Baiting was effectively a sport where dogs were sent in to immobilize a bull, some even believed the sport caused the meat of the bull to be more tender. By the 16th Century just about every town in England had a Bull Baiting ring. At one time in England, it was even illegal to sell the meat of Bull that was not Baited in the Ring.

Due to the popularity of Dog Sporting events (however, cruel) during this time, the sport of Ratting and Dog fighting was started. It is presumed that the sport was popular because it gave people of low means another possible way of providing for there families. The sport of ratting was where a Dog was placed in a Pit with Rats, the dog would kill as many as possible during a set period of time. The dog who killed the most won. It is this sport that is believed to be the reason why the Bull dogs and terriers of England were mixed, attempting to combine the strength of the bull dog with the gameness of the terrier. It is believed that the "pit" in pit bull comes from the ratting pit.

In 1835 the sport of Bull Baiting and Dog Fighting, were made illegal under English Law. However, due to the ease of concealing Dog Fights, it is believed that Dog Fighting continued for the most part un-restricted in many parts of England. This increased the Popularity of the Ratting sport.

When the English and Irish immigrants came to America, they brought there dogs with them. One of the most popular being the close relative of the Modern day American Pit Bull Terrier. Unfortunately dog fighting continued to be popular in America through the 19th century. In addition to dog fighting the Pit Bull continued to get a name for itself by being a very versatile all-purpose dog. Known to be able to Herd sheep and Cattle, the pit bull found a home with many early settlers of America.

In 1884 the American Kennel Club was formed for the purpose of promoting purebred dogs and their owners. Unfortunately, due to the illegal nature of Dog Fighting, the American Kennel Club, refused to accept the Pit Bull Terrier as a full blood breed. This is why in 1898 the United Kennel Club was formed, with the goal to certify dogs that were uncertifiable by the AKC, the first breed of dogs recognized by the UKC was the "American Pit Bull Terrier".

To add to the confusion of the breed the AKC decided in 1936 to recognize the American Pit Bull Terrier but under a different name, the Staffordshire Terrier, named after the area in England where they suspected the original crossbreeding took place. Later the term American was added to the Staffordshire Terrier in order to avoid confusion with the smaller cousin being raised in England.

The American Staffordshire Terrier, or the Amstaff, has had different blood lines from the UKC American Pit Bull Terrier, since 1936. However, it is possible for a AKC Amstaff to be double registered as a AKC Amstaff and as a UKC Pit bull, it is not possible for a dog that was originally titled a UKC Pit bull to be recognized by the AKC as a Amstaff. Thus adding to the confusion, it is however commonly accepted that the Amstaff and the APBT share a common ancestry, however the Amstaff today appear to look the same however, tends to be on average 10 pounds or so lighter than the APBT. This likely happened because UKC breeders continued to breed a dog suitable for working dog competitions, where as the Amstaff was and is breed to be more of a show dog.