The Boston terrier breed originated around 1875, when Robert C. Hooper of Boston purchased from Edward Burnett a dog named Judge (known later as Hooper's Judge), which was of a bull and terrier type lineage. Hooper's Judge is directly related to the original bull and terrier breeds of the 19th and early 20th centuries. The American Kennel Club cites Hooper's Judge as the ancestor of all true modern Boston Terriers.
The Boston Terrier's large, prominent pair of eyes is a distinguishable feature. The breed's round eyes are set widely apart, are large in size, and located squarely in the skull. The breed's genetic makeup produces a short tail. These short tails can take the shape of a corkscrew, or curl, or they can be straight. Generally, Boston Terriers' tails do not exceed 2 inches (51 mm) in length.
Curvature of the back, called roaching, might be caused by patella problems with the rear legs, which in turn causes the dog to lean forward onto the forelegs. This might also just be a structural fault with little consequence to the dog. Due to their shortened muzzles, many Boston Terriers cannot tolerate excessively hot or cold weather and demanding exercise under such conditions can cause them harm. A sensitive digestive system is also typical of Boston Terriers with flatulence commonly being associated with poor diet in the breed.
Their large and prominent eyes make Boston Terriers prone to corneal ulcers. Due to the breed being characterized by a short muzzle paired with a large pair of eyes, their eyes are susceptible to injury when making contact with sand, dust, debris, or sharp objects, such as plants with thorns.
Boston Terriers are brachycephalic, meaning that their head is both broad and short, resulting in small nostrils, long palates and a narrow trachea; the shortened nose of brachycephalic animals can lead to brachycephalic airway obstructive syndrome. Bostons may be prone to snoring and reverse sneeze—a rapid and repeated forced inhalation through the nose—accompanied by snorting or gagging sounds used to clear the palate of mucus, which does not harm the dog if it does not last for more than 1–2 minutes. Brachycephalic dogs may be prone to complications with general anesthesia.
Bostons frequently require caesarean section to give birth, with over 80% of litters in a UK Kennel Club survey delivered this way.