The Blue Paul Terrier, which looks a lot like the pit dogs of our day and age, is unfortunately extinct. They used to be powerful dogs, yet could not survive into the 20th century, mainly due to lack of selective breeding in the United States as well as in European countries. Additionally, these dogs were made to fight each other till death since they had extraordinary fighting skills, which may have led to a great decline in their numbers. Where they came from has been a point of debate even when they existed and where they have gone seems to have become another mystery of modern times.

The Blue Paul Terrier was a strong, athletic and powerful dog. It had a short smooth coat of fur, like many other pit dogs of today. As the name suggests, the color of the coat was deep blue, not unlike some of the greyhounds of today. In some cases, there were shades of other colors present, mainly red, known as smuts in Scotland, where they were known to have existed. Paul is included in the name of this dog since it is widely believed that John Paul Jones, a sailor, first brought this dog to the USA in 1777.

Their height, which has been documented, came up to about 50 centimeters. They were known to weigh about 20 kilos in adulthood. Their head tended to look a little large for their bodies. They also had a flat forehead, which is typical of modern pit dogs. But, unlike modern bulldogs, their muscles did not recede. Instead they tended to be broad and large as well as square. They had a very even set of teeth, with no flews hanging over. There used to be a slight dip in the forehead, just between their eyes.

The eyes of the Blue Paul Terrier used to be a dark shade of hazel. Also, they tended not to be sunken like many other bulldogs. The eyebrows of the Blue Paul Terrier had the ability to knit and contract, giving them a whole range of expressions one rarely sees in purebred dogs. The only dogs known to have expressive faces are usually hybrid dogs, who inherit different sets of musculature from each parent. The ears of the Blue Paul Terrier were also rather distinctive. To begin with, they were quite small, but were held upright and they tended to be thin. More often than not, their ears tended to be cropped.

The body of the Blue Paul terrier was considered round, but muscular. It had a deep chest cavity, which was also wide, giving the dog a rounded look. Its back was short and broad, adding to the feeling of roundedness. The tail of the Blue Paul terrier always tended to be low, so low that it could never be raised above the height of the back. The tail did not have any fringe.

The Blue Paul terrier could stand firm and straight on the ground on all four paws. All its legs were strong. The front legs were not curvy in the least; instead they were muscular and stout. The hind legs were also equally muscular and strong.