Historians of American slavery are well-aware that there were slaves in New Netherland before the Dutch colony’s surrender to the English in 1664. It is seldom recognized, however, that the Dutch-speaking slave population in New York grew during the next century. This article establishes for the first time a reasonable estimate of the total number of Dutch-speaking slaves who lived in New York during the eighteenth century. To estimate the cumulative size of a dynamic population over time, the author constructs a population growth model with data drawn from New York’s colonial censuses, slave import and export data, and birth and death rates based on comparable historical circumstances, along with assumptions of exogenous shocks to the population due to factors such as war and slave runaways. The model suggests the total number of slaves who lived in New York at any point in the eighteenth century probably reached around 76,000. The article argues further that from 22,800 to 30,000 (30 to 40%) of these slaves likely spoke some Dutch.