Using Census Districts in Analysis, Record Linkage, and Sampling The United States Census Bureau, in order to facilitate the process of enumeration, has divided larger political units (states, counties, or cities) into more manageable ones. In the censuses between 1850 and 1870 these units of enumeration were known as subdivisions; later they were referred to as enumeration districts. The manuscript schedules between i850 and 1900 indicate the enumeration district or subdivision on each page. The purpose of this note is to call attention to three distinct ways in which these small geographical units can be put to good use by historians using manuscript census schedules. First, small spatial units of analysis are valuable for the study of geographical patterns within a city or county. Second, they make the task of locating a specific individual in the census schedules much easier than it has been. And third, they can be used to draw with ease a truly random sample from census schedules. I have limited my discussion to the census schedules of I850 and after because from that date a valuable source, which has only rarely been exploited by historians, is available: the boundaries of the subdivisions and enumeration districts. The Cartographic Division of the National Archives has preserved the boundary descriptions from I850 to i880 and the maps on which the boundaries are indicated for I900 (the I890 census schedules were destroyed in a fire). The I880 collection is incomplete but it includes the boundaries for thirty-six states and territories, including those for thirteen of the fifteen most populous states.1 Many state census manuscripts are, like the federal census schedules, subdivided into smaller units of enumeration, and it is