The Cavalier King Charles Spaniel is a small spaniel classed as a toy dog by The Kennel Club and the American Kennel Club, that originated in the United Kingdom. Since 2000, it has grown in popularity in the United States and ranks as the 19th most popular pure-breed in the United States. It has a silky, smooth coat and commonly a smooth undocked tail. The breed standard recognises four colours: Blenheim (chestnut and white), Tricolour (black/white/tan), Black and Tan, and Ruby. The breed is generally friendly, affectionate and good with both children and other animals; however, they require a lot of human interaction. Since they are a family dog, it is recommended to not leave them alone for long periods at a time. The expected average lifespan of a Cavalier King Charles Spaniel is under ten years.The Cavalier King Charles changed dramatically in the late 17th century, when it was interbred with flat-nosed breeds. Until the 1920s, the Cavalier shared the same history as the smaller King Charles Spaniel. Breeders attempted to recreate what they considered to be the original configuration of the breed, a dog resembling Charles II's King Charles Spaniel of the Restoration. Various health issues affect this particular breed.