Map Guide to the U.S. Federal Censuses, Iowa 1840-1920 Map Packet; by William Thorndale & William Dollarhide; 4 sheets; 8.5x11; Item # A0021.
The county has always been used as the basic Federal census unit. Genealogical research in the census, therefore, begins with identifying the correct county jurisdictions. This Iowa Map Packet shows all U.S. county boundaries as they were at the time of the U.S. Decennial Census from 1840 to 1920. On each sheet the old county lines are superimposed over the modern ones to highlight the boundary changes at ten-year intervals.
With each map there is data on boundary changes, notes about the census, and locality finding keys. There also are inset maps that clarify territorial lines, while the detail in this work is exhaustive and of impeccable standards.