The development of the breed began in the late 1950's with the importation of a small number of haired sheep from the Caribbena by Michael Piel of Maine. The Piel Farm had several thousand sheep at the time and Piel felt that "progress in selection for traits important to the production of meat would be greatly enhanced by the elimination of wool as a major factor for selection." His goal was to combine the hair coat, prolificacy, and hardiness of the Virgin Island sheep with the meat conformation and rate of growth of wool breeds. He began to experiment with crosses between the hair sheep and carious British breeds, especially Suffolk. After almost 20 years of crossing the resulting hybrids "in every conceivable combination" and selecting the individuals with the desired combination of traits, Piel eventually collected a flock of ewes he called Katahdins, named after Mt. Katahdin in Maine. During the mid 1970's the Wiltshire Horn, a shedding breed from England, was incorporated into the flock to add size and improve carcass quality.

From this original flock, new breeders have been able to expand the number of Katahdin sheep in North America and many other countries, and select carefully for hair coat, carcass quality, and reproductive efficency. In 1986, a breeders organization, Katahdin Hair Sheep International (KHSI) was formed. Its purposes are to: studies of internal parasite tolerance in Arkansas indicate that Katahdin sheep possess a significantly higher degree of parasite resistance than wool sheep that they were compared to. Heat tolerance trials demonstrated a similar relationship. Other traits being studies at research institutions include out-of-season breeding, prolificacy and fertility factors, carcass quality, and meat flavor, and growth performance.

Katahdins are a heavy muscled, medium-sized breed. They demonstrate adaptability by performing well in areas varying in geography, temperature, and humidity, feed and forage resources, and management systems. Ewes are easy lambers, and exhibit strong maternal instincts and good milking ability. They possess high potential for early puberty, fertility, and lamb survivability. Lambs grow and mature rapidly to an acceptable market weight range and produce relatively lean and well muscled carcasses with a very mild flavor.

Ewes and rams exhibit early puberty and generally have a long productive life. Mature ewes usually have twins, occasionally producing triplets and quadruplets. A well-managed and selected flock should produce a 200% lamb crop. Rams are agressive breeders, generally fertile year round, and can settle a large number of ewes in the first cycle of exposure. With selection a flock can consistently lamb throughout the year.