Page:Geographic Areas Reference Manual (GARM).pdf/245

 These sanitary districts then were used to analyze and compare the effect of population, topography, and housing on the mortality rate of the inhabitants. The delineation of these sanitary districts was an important step in the evolution of geographic statistical entities. This may have been the first instance of Federal and local cooperation in designing a set of small geographic units based on population and housing characteristics.

In 1906 Dr. Walter Laidlaw, Director of the Population Research Bureau of the New York Federation of Churches, published an article putting forth the idea of delineating and using small geographic areas as a method of studying neighborhoods in New York city. Dr. Laidlaw had been studying neighborhoods by using the 1900 census data for assembly districts (subdivisions of New York city’s boroughs) together with information from other sources. In 1905, the State of New York changed the boundaries of the assembly districts, thereby altering the geographic framework and impairing the usefulness of all his information.

In search of a solution, Dr. Laidlaw proposed a scheme that did away with both ward and assembly districts as data tabulation units. Instead of these, he suggested the delineation of permanent small areas that would retain their boundaries from census to census. His plan was to subdivide each square mile of New York city into quarter sections of about 160 acres. In 1909, he persuaded the Census Office to adopt the concept, and they collected the 1910 census data in a manner that allowed for these tabulations by small area. Interested data users then could purchase the data summaries and arrange for their tabulation and publication. The Census Office also delineated similar districts, later called census tracts, in seven other cities: Baltimore, Boston, Cleveland, Chicago, Philadelphia, Pittsburgh, and St. Louis.

The Census Bureau collected data by census tract for these eight cities in 1910 and 1920; however, only New York city made immediate use of the data. In the mid-1920s, Chicago and Cleveland purchased and published their census tract data. By the end of the decade, 18 cities (the same 8, Notes and References 10-2Census Tracts and Block Numbering Areas