The Khoikhoi people who lived in the Cape Peninsula when the Dutch began trading with the area during the mid 17th century, had a hunting dog which was described as ugly, but noted for its ferocity when acting as a guard dog. This dog measured approximately 18 inches (46 cm) at the withers, with a lean but muscular frame. The ears have been described both as erect and hanging, but the most distinctive feature was the length of hair often growing in the reverse direction along its back. Within 53 years of Dutch colonisation in Southern Africa and the origins of the wagon-trekking boers later known as Afrikaners, who converted vast stretches of wild veld into farmland, hunted for meat and defended their cattle herds, staff, and homesteads from lion, the Europeans were using these local dogs themselves.
By the 1860s, European colonisers had also imported a variety of mainly European dog breeds to this area of Africa, including such dedicated hunting dogs as Great Danes, Bloodhounds, Greyhounds, and terriers. Other breeds came from Arabian traders around the Horn of Africa and with Asian immigrants, particularly into the Cape Colony, and jackal coursing introduced from British India brought lurchers from England and Ireland and the borzoi or Russian wolfhound, and before the era of standardised modern breeds, several breeds may have more rarely contributed to Rhodesian ridgeback genetics. Van Rooyen saw Helm's pair of bitches and decided to breed his own dogs with them to incorporate their guarding abilities. It is not known if these two first direct ancestors of Rhodesian ridgebacks had dorsal hair pattern ridges themselves, but they founded the Rhodesian ridgeback bloodline, so either carried the trait or it was added from other Boer dogs and hybrids with Khoikhoi ridgebacks which van Rooyen bred into his lines over many trials then generations.
After trying pointers and Airedales, crossing with collies gave van Rooyen the best lion hunters, as his son Cornelis Jr. tells us. Pointers, bulldogs (perhaps boerboels, which were actually mainly larger mastiffs) and greyhounds are generally credited in the European core of this mix, with larger terriers such as Irish terriers and perhaps great Danes. Modern Rhodesian ridgeback breeders speak of some of their ridgebacks being too 'mastiffy' though it is uncertain what extent, if any, of actual mastiff heredity may have entered, as from the boerboels and their descendants prevalent in these territories. After initially greyer, rough-coated litters originating from Helm's dogs, van Rooyen's subsequently crossed offspring turned to redder coats, incorporating the KhoiKhoi landrace dog's ridges already carried in Boer dogs within his genomes. They became the foundation stock of a kennel which developed dogs over the next 35 years with the ability to bay lions: that is, a pack of 4-6 Rhodesian ridgebacks holds lions at bay while the hunter makes the kill, though an individual Rhodesian ridgeback is no match for an adult lion in a fight. These dogs were used to hunt not only lions but also other game, including wild pigs and baboons, and they can kill a baboon independently of a human hunter's collaboration.
The original breed standard for the Rhodesian Lion Dog was drafted in 1922 by F. R. Barnes on founding the first Ridgeback Club at a Bulawayo Kennel Club show, then in Southern Rhodesia (now in Zimbabwe), and based on that of the Dalmatian. In 1927, Barnes' standard was approved by the South African Kennel Union with the name amended to Rhodesian ridgeback. Outside the subcontinent and internationally, the first Rhodesian ridgebacks in Britain were shown by Mrs. Edward Foljambe in 1928. In 1950, 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 Margaret Lowthian of California began the process of getting the breed accepted by the American Kennel Club. Similarly, in 1952, The Rhodesian Ridgeback Club of Great Britain was founded at Crufts to promote the breed around the United Kingdom to show judges, so a standard for the breed might be recognised. In 1954 the first Challenge Certificates were awarded to dogs shown as Rhodesian ridgebacks at United Kingdom competitions, toward their subsequent recognition by The Kennel Club of Great Britain, and in 1955 the American Kennel Club recognised the Rhodesian ridgeback breed as a member of the hound group.