The Polypay was developed at the United States Sheep Experiment Station in Dubois, Idaho beginning in the late 1960’s.  Researchers drew from four breeds: Finnish Landrace, Rambouillet, Targhee and Dorset, to produce a prolific sheep that would lamb out of season and produce a fast-growing lamb and high-yielding carcass.  The breed was fixed in 1975 and has since spread to farms across the United States, Canada and Mexico.  Polypay lambs are good feeders and grow quickly and steadily to 36 kg.  They are docile, easily managed and thrive in pasture, rotational grazing and confinement systems.