The object of this essay has been to help examine spatiotemporal variation in literacy. The research reported here centered on the Valley of Oaxaca, an agricultural region in southern Mexico, during the period from 1890 to 1980. The data consist of a systematic compilation of tax and voting lists from the nineteenth century, census responses from 1890 to 1980, community ethnographies, published histories and biographies, and government reports. Attending to both the spatial and the temporal scales of events and causes was methodologically important for this research.