We know remarkably little about the length of the working day before the 1880s. In this paper, we summarize what is known about the trend in the length of the workday in American manufacturing industry from 1830 to 1890. We than develop estimates of the daily hours of work and form the basis for our on-going research into the performance and operation of the industrial labor market in America in the late nineteenth century. We conclude on the basis of our firm-level sample data that the average workday in American manufacturing industry in 1880 was almost exactly ten hours, placing the attainment of the ten-hour day almost a decade earlier than hitherto supposed. Despite the decline in hours to 1880, however, daily hours of work were still long enough that they would have required the use of artificial light in most factories during the winter. Our statistical analysis also reveals and documents small but statistically variations in hours between firms and industries and between regions and by location.
