The Newfoundlands have webbed feet and a water-resistant coat. Males normally weigh 60–70 kg (130–150 lb), and females 45–55 kg (100–120 lb), placing them in the “Giant” weight range but some Newfoundland dogs have been known to weigh over 90 kg (200 lb) – and the largest on record weighed 120 kg (260 lbs) and measured over 6 feet (1.82 m) from nose to tail, ranking it among the biggest Molossers. They may grow up to 22–30 inches (55–71 cm) tall at the shoulder.
The Newfoundland shares many traits with other mastiffs, such as the St. Bernard and English mastiff, including stout legs, massive heads with very broad snouts, a thick bull neck, and a very sturdy bone structure. In fact, many St. Bernard Dogs have Newfoundland Dog ancestry. Newfoundlands were brought and introduced to the St. Bernard breed in the 18th century when the population was threatened by an epidemic of distemper. They share many characteristics of many mountain dog breeds such as the Great Pyrenees.
The Newfoundland breed originated in Newfoundland, and is descended from a breed indigenous to the island known as the lesser Newfoundland, or St. John’s Dog. The mastiff characteristics of the Newfoundland are likely a result of breeding with Portuguese Mastiffs brought to the island by Portuguese fishermen beginning in the 16th century.