Question from a newsletter reader: "On the 1910 census, the first 3 columns are numbers, such as 52,28,39. Can you tell what these are? I tried US Census & Archives to no avail. Thanks."
Answer: House number, Number of dwelling house (in order of visitation), and number of family (in order of visitation).
For more information, see http://usa.ipums.org/usa/voliii/inst1910.shtml and start at paragraph #91. An image of the top part of the census form can also be found at http://freepages.genealogy.rootsweb.ancestry.com/~vadennison/graphics/1910_headings.jpg