There were two enumerations of Manhattan, then "New York City" in 1870. The second enumeration in late fall of 1870 included street names and addresses. The problem has been that the definitions changed for Wards/Election Districts between the first and second enumerations, and apparently there was no resource material online to figure out from an address what Ward/Election District an address was in.
The NY Public Library had a Ward/Election District map for the 2nd enumeration of 1870 for public view, and I had a volunteer photograph it today. Then I started searching for 1870 NYC maps, and amazingly, found the same map online.http://upload.wikimedia.org/wikipedia/commons/f/f7/1870_Hard...
The main (bottom) map is what we want. The large red numbers appear to be the Ward numbers. Within each ward the blocks that make up an Election District are color coded and one block has the district number in small black type.
Dana Point, CA