This study examines the factors that influence the location of manufacturing industries in Alberta, Saskatchewan and Manitoba. Location factors are analysed in terms of spatial decision-making at three geographical scales. These are the Prairies as a whole, individual Prairie provinces, and specific cities or communities. The significance of the organizational structure and internal operating policies of manufacturing enterprises in influencing industrial location is investigated. Three approaches are adopted for the study. A historical analysis indicates that the geography of Prairie manufacturing is related to proximity to material inputs and internal markets, railway freight rates and certain regional advantages which are not explicit, but nevertheless evident, as a consequence of export-oriented firms locating in the region. The second approach is a quantitative analysis of location factors. Shift-share data indicates that markets and resources contribute to the development of, and shifts in, Prairie manufacturing employment. Spatial correlation between 1970 manufacturing employment and 13 economic variables suggest that manufacturing is spatially associated with the market as represented by population and retail sales. An analysis of the population thresholds necessary for manufacturing provides further explanation of the significance of market elements in relation to the location of manufacturing activities in cities. Within Prairie cities the location of manufacturing activity is not entirely market-oriented. The findings of the historical and quantitative analyses are generally substantiated by an empirical investigation of location decision-making of Prairie manufacturing enterprises...