For many home computer enthusiasts of the 1980s and 1990s, a local dial-up bulletin board system, or BBS, provided the first opportunity to get online, chat with strangers, share files, and play games. But how many is “many”? Was BBSing limited to a few elite geeks, or did it reach broader populations? Lacking any central record-keeping authority, the demography of dial-up BBSs is difficult to ascertain. To estimate the number of systems and the size of the user population, this study draws on a mix of incomplete sources. Regional lists of bulletin board systems indicate the geographic growth of the decentralized BBS network; a questionnaire circulated by the U.S. Census reveals a partial snapshot of the user population; and market statistics published in the trade press reflect its commercial expansion. In spite of their limitations, a statistical analysis of these data provides a first-order approximation of North American BBS demographics, suggesting a scale comparable to better-known contemporary systems such as ARPANET or CompuServe. Further development of this methodology will enable the production of historical demography across networks, regions, platforms, and language groups.