This book uses the published compensation of US postmasters to find the revenues of each post office through most of the nineteenth century, providing a proxy for economic activity in the area served by each post office for every two-year period. This disaggregated, high-frequency measure of economic activity makes it possible to see, for example, the impact of railway construction on economic activity or the way in which business cycles differed across regions. Data on postmasters and their compensation also provide insight into social mobility and status, with emphasis on female and African American postmasters and on the transmission of postmaster positions within families.