The Rhodesian Ridgeback is a dog breed developed in South Africa. Its European forebears can be traced to the early pioneers of the Cape Colony of southern Africa, who crossed their dogs with the semi-domesticated, ridged hunting dogs of the Khoikhol.
In the earlier parts of its history, the Rhodesian Ridgeback has also been known as Van Rooyer's Lion Dog, the African Lion Hound or African Lion Dog - Simba Inja in Ndebele, Shumba Imbwa in Shona - because of its ability to keep a lion at bay while awaiting its master to make the kill.
The original breed standard was drafted by F.R.Barnes, in Bulawayo, Southern Rhodesia (now Zimbabwe), in 1922. Based on that of the Dalmatian, the standard was approved by the South African Kennel Union in 1927.
The distinguishing feature of this dog is the ridge of hair running along its back in the opposite direction from the rest of its coat. It consists of a fan-like area formed by two whorls of hair (called 'crowns') and tapers from immediately behind the shoulders down to the level of the hips. The ridge is usually about 2 inches (5 cm)in width at its widest point. It is believed to originate from the dog used by the original African dog population which had a similar ridge. The first depiction of a Ridgeback is a wall painting describing the life of the Boers, housed in South Africa in the Voortrekker Monument.
This is a painting of a Rhodesian Ridgeback, by Carl Friedrich Schultz (1796-1866).
This clearly shows the ridge on the dog's back:
The first Rhodesian Ridgeback in Britain was shown by Mrs Edward Foljambe in 1928. Mr and Mrs William H. O'Brien of Arizona brought six carefully selected Ridgebacks to the US from South Africa. He and his wife and Mrs Margaret Lowthian of Calfornia began the process of getting the breed accepted by the American Kennel Club. The breed was admitted into the American Kennel Club in 1955 as a member of the Hound Group.
The original standard allowed for a variety of coat colours, including brindle and sable. The modern FCI standards calls for light wheaten to red wheaten.
Other dog breeds also have a reverse line of fur along the spine, including the Phi Quoc Ridgeback dog and the Thai Ridgeback. The Thai Ridgeback is a crossbreed of the Phu Quoc; historians have speculated the relationship between the Rhodesian Ridgeback and the Phu Quoc with suggestions that historically one breed may have been imported to the other's location.
Thanks again to the information I found on Wikipedia.