Technical Abstract: Few long-term selection studies for production have been conducted with dual-purpose Western range sheep in the U.S. The objective of this study was to document and compare genetic trends in production traits of three dual-purpose breeds of sheep (Rambouillet, Columbia and Targhee) at the United States Sheep Experiment Station (USSES), Dubois, ID, over a 49-yr period (1950-1998). Selection was based on weaning performance under range conditions. Genetic trends in production traits of the Polypay breed, over a 22-yr period (1977-1998), also, were documented and compared with the other three breeds over the same 22-yr period. The production traits examined included prolificacy, weight, and wool traits. Prolificacy, weight and wool data were from sheep born at the United States Sheep Experiment Station, Dubois, Idaho. For the Rambouillet (RAM), Columbia (COL), and Targhee (TAR) breeds, data from 1950 to 1998 were included in the analyses and for the Polypay (POL) breed, data from 1977 to 1998 were included. The results indicate that genetic improvement in prolificacy and growth traits can be made over long periods of time in flocks of dual-purpose breeds undergoing selection for weaning performance. Positive genetic correlations for litter size weaned with litter size born and weaning weight at 120 d with birth weight resulted in desirable correlated progress in all of the traits. Wool traits were not significantly adversely affected over the long period of time due to near zero correlations between weaning performance and wool traits. Management practices, such as restricting the number of lambs that a ewe can raise, may negatively impact the rate of genetic progress in weaning performance in highly prolific breeds.