The Blue Paul Terrier resembled our contemporary pit dogs. They had a smooth coat and were powerfully built. They weighed about 20 kg and measured up to 50 cm at the withers. The head was large; the forehead was flat, muscle short and square, large and broad but not receding like that of the Bulldog. The jaws and teeth were even with no overchanging flews. They had a slight dip between the eyes, which were dark hazel and not sunken, prominent, nor showing haw. The ears were small, thin, set on high, and invariably cropped, and the face was not wrinkled. The eyebrows contracted or knit. The facial expression of the Blue Paul has never been seen in any other breed and can frequently be recognized in mixed-breed dogs.[clarification needed] The body was round and well ribbed up, its back short, broad, and muscular but not roached, and its chest deep and wide. The tail was set low and devoid of fringe, rather drooping and never rising above the back. The dog stood straight and firmly on its legs. Its forelegs were stout and muscular, showing no curve. The hind legs were very thick and strong, with well-developed muscles. The colour was dark blue as can be seen in Greyhounds; however, they sometimes produced brindles or reds, which were known as red smuts in Scotland.
No one seems to have full knowledge as to how the Blue Pauls were bred or from where they originally came. There was a story that Paul Jones, the pirate, brought them from abroad and landed some when he visited his native town of Kirkcudbright about 1770. The gypsies around the Kirkintilloch district kept Blue Pauls, which they fought for their own amusement. They were game to the death and could suffer much punishment. They were expert and tricky in their fighting tactics, which made them great favorites with those who indulged in this sport. They maintained that the breed originally came from the Galloway coast, which lends support to the Paul Jones legend. The first dogs to arrive in the United States with the English immigrants in the mid-19th century were the Blue Paul Terrier and the Bull and Terrier.