In the twenty years surrounding the turn of the twentieth century, the form and character of agricultural buildings in the Northern Rockies and the construction methods used to build them changed dramatically. This essay focuses on the Gallatin Valley of southwestern Montana to explore the nature and meaning of these changes. It places them within the context of the region's growth and development during its early agricultural settlement, which coincided with a period of tremendous advances in agricultural practices. The earliest Euro-American buildings in the region (1862 to the 1880s) reflect typical frontier construction, with logs the predominant material due to the plentiful local pine and fir and the limited tools available. However, this construction method presented structural limitations when the need for larger buildings arose due to regional economic development. Lacking other alternatives, farmers and stock growers put their faith in light balloon frame construction, although many of them had little experience with this method, particularly for sizable buildings. The demand for larger and more complex buildings spurred the introduction and subsequent adoption of an essentially new architecture. High elevation, climate, and the forces of national economic markets were the principal factors that influenced the rapid transition to light wood framing in Rocky Mountain agricultural buildings. This transformation, a real revolution in local design and construction, relates to the larger history of American architecture in the western United States, and it led to the broad diversification of farm building forms and types in the Northern Rockies.