This paper explains how technological developments and changes in production encouraged and drove the processes of agricultural modernisation that occurred in the second half of the twentieth century, taking the region of Aragon in north eastern Spain as a case study. The main agricultural macro-variables reveal a surge in output, coincident with a far-reaching restructuring of production, in which livestock and animal feeds played a key role. The relative success of this high speed agricultural transformation was largely due to technological progress and the development of Aragon's trade links before 1936. Meanwhile, the earlier development of irrigation schemes, the capitalisation of farms and experimentation with different seed varieties allowed the region to adapt quickly to the new Green Revolution technologies that came to the fore after 1950. At the same time, established trade links allowed a swift transition to livestock and related produce destined for fast developing agro-industrial regions, like Catalonia and Valencia. As in other countries, technological and trade path dependency also explain the polarisation of agricultural development within Aragon itself, and in particular the success of the provinces of Zaragoza and Huesca in contrast to failure and depopulation in Teruel. The experience of Aragon may thus be useful to understand the dynamics of other less developed regions currently in the throes of transformation.