The discovery by Vernon B. Mountcastle of the columnar organization of the cerebral cortex (Mountcastle VB, J Neurophysiol 20:408-434, 1957, Brain 120:701-722, 1997) was the single most important discovery of the twentieth century in cortical physiology. Not only did it serve as the framework for the orderly arrangement of knowledge concerning cortical organization and function (Edelman and Mountcastle, The mindful brain. MIT Press, Cambridge, MA, 1978) but also as a framework for exploring and investigating new ideas and for revisiting old ones about the organization of particular cortical areas. Here I review the history of facts and ideas about the organization of the motor cortex and discuss the evidence that the direction of movement is the principle governing motor cortical columnar organization.