THE ZONING SURVEY 49 



been made of the distribution of the population of the city. The spot map 

 was of great assistance in comprehending at a glance the distribution of 

 population throughout the city and in estimating the relative effect of various 

 kinds of transit facilities on the distribution of population. (See Figure 20.) 



Supplementing the census data as to distribution of population in their 

 places of abode, data was obtained and charted to show the distribution of 

 factory workers in the places in which they work. At the request of the 

 Commission, the State Labor Department compiled from its records a block 

 census for all factory employees throughout the city according to place of 

 work. With this data the Commission prepared a spot map of factory 

 employees — one spot for each 250 employees. This map was valuable in 

 laying out the unrestricted or industrial districts and in studying the exist- 

 ing and possible future relation between congestion of factories and con- 

 gestion of population. (See Figure 7.) 



The results of the police census of 1915 were plotted by census districts 

 and the center of gravity of the population of each district obtained, and 

 from these the center of gravity of the population of each borough. These 

 were combined to obtain the center of gravity of the population of the 

 entire city. This map enables one to see the relation of these several centers 

 of population to existing business and traffic centers. (See Figure 28.) 



Existing building development 



The entire zone plan as proposed by the Commission is based on a 

 frank acceptance of existing conditions. The zone plan not only does not 

 affect the continued use of any existing building, but it ordinarily does 

 not attempt to radically change the character of new buildings from the 

 type with which any considerable area is at present built up. It was very 

 important, therefore, that the Commission should have before it a detailed 

 record of the existing building development in every part of the city. (Fig. 

 30.) 



Distribution of buildings according to use 



In order to study the location of existing residential, business and 

 industrial buildings and areas, borough maps were prepared showing in 

 colors industrial buildings and use, business buildings, store and dwelling 

 buildings and residential buildings, including under the latter head schools, 

 churches and institutional buildings. These maps enabled the Commission 

 to determine the general boundaries of the residence, business and unre- 

 stricted districts, in so far as such boundaries could properly be based on 

 the existing building development. 



The Commission based its work, however, not entirely or chiefly on 

 existing building development, but also upon its judgment of future growth 

 and requirements. In order to better judge the future growth and change 

 of the business, residence and industrial areas a careful study was made of 

 such growth and change in the past. Based on information given in the 



