The story of the Coopworth began after World War II at Lincoln College in New Zealand when faculty member, Dr. Ian Coop, accepted the challenge which was to be his lifetime accomplishment: increasing lambing percentages in the national flock. The two leading breeds at the time were Border Leicester and Romney. Both researchers and farmers agreed that the weak link in the NZ sheep industry was ewe prolificacy, so improving lambing percentages was established as a prime research objective with wool quality and hardiness also deemed essential.
Initial experiments showed that the F1 ewe from a Border Leicester/Romney cross did bear significantly more lambs than either parent breed. But could that advantage be fixed in a stabilized breed? Twenty years of crossing, interbreeding, performance recording and rigorous selection were to follow. It was in 1963 that the resulting new breed was officially named Coopworth and the Coopworth Sheep Society of New Zealand was founded. The breed philosophy was to continually select for measurable, performance-based traits rather than appearance alone. Designated traits include growth rate, fertility and wool production.
There were several large importations of white and natural colored Coopworth sheep into the United States and Canada in the 1970's and 1980's. These sheep were destined for both large, commercial operations and smaller homesteads and niche market producers. Due to restrictions on live animal importation today, artificial breeding is now used to obtain genetic diversity and continued improvement of the breed.