This article traces the development and expansion of early computer systems for managing and disseminating ‘real-time’ market data at the most influential stock market in the United States, the New York Stock Exchange (NYSE). It follows electronic media at the NYSE over a roughly ten-year period, from the time of the deployment of a computer called the Market Data System (MDS) through debates surrounding the National Market System and the passage of the 1975 Securities Acts Amendments. Building on research at the archives of the NYSE and the Securities and Exchange Commission (SEC), this history emphasizes the regulatory and managerial contexts in which market data became computerized. The SEC viewed market automation as both necessary for the viability of the securities industry and a mechanism for expanding regulatory oversight over the venues of stock trading. Moving from the MDS to later technical projects in the late 1960s and early 1970s, this article charts the changing meaning of electronic governance in a market increasingly conceptualized as a technical object. Adding to recent work in the social studies of finance and financial technologies, this history sites early NYSE computerization programs within managerial efforts to consolidate control over the clerical labor of financial markets, and in contests between regulatory and market institutions. It concludes by exploring the differing forms of electronic governance activated in these efforts to bring computers into the market.