In this article, I consider the question: why did numeracy become a relevant and sensible thing to consider in mathematics education? I historicize the numeracy discourse by writing a genealogy of how the concept of "numeracy" emerged in scholarship, with a focus on the USA. I argue that numeracy descends from three mathematics education reform narratives and emerged, in part, as a compromise among these narratives. The numeracy discourse unites reform narratives about technological change, equity and justice, and social stability. I find these narratives in the numeracy discourse and describe them as "promises"--or assurances about the present and future--central in the numeracy discourse: (1) numeracy promises to reflect modern reality, (2) numeracy promises to empower, and (3) innumeracy promises to have social costs. These three promises seem to each emerge from different conceptualizations of the importance of numeracy and the purposes of reform in its name. Finally, I consider the purposes of genealogy by discussing my current thinking about numeracy.