According to the Saint Bernard Club of America, the dogs that would eventually become the Saint Bernard breed were sometimes referred to as alpine mastiffs. The monastery located at the Great Saint Bernard Pass in the Alps has used mastiff-type dogs for rescue work for several centuries.
The dogs are probably descendants of mastiff-type dogs left behind by the Romans. The monastery began breeding the dogs for rescue work starting around 1660. The winters of 1816-1818 were severe and killed off most of the original breed. Other breeds, such as Leonbergers, may have been mixed with the original strain in the 19th century. The breed was finally named "Saint Bernard" in 1880.