The role of the agricultural sector in economic growth has recently come under study. Numerous articles have appeared on the theoretical aspects (capital formation, increased productivity, etc.) of agriculture's contribution as well as on the numerical magnitude of changes that have taken place. These studies, together with many historical writings on the growth of American agriculture, raise the possibility of several hypotheses about the specific role of agriculture in American economic growth. Recently the work of Rasmussen (9) has presented a hypothesis which deserves examination.1 Rasmussen finds that the statistical record shows two periods of "revolutionary" change in the agriculture sector : 1850 to 1870 and 1940 to the present time. He notes that these were periods of radical changes in the sources of farm power; they appear as periods of sharp increases in both output and productivity. Specific changes in technology and the nature of demand are shown to have had given effects on the nature of production; hence, upon the structure of the sector. This article examines the theory underlying the concept of "agricultural revolution." That is, the usage of this term, previously and presently, is examined in the light of recent work in the field of development theory and economic history.