Reconstruction of the social composition and assessment of the changing size of past communities are basic tasks for the historian of local communities. Not only is the demographic pattern of a community of central significance in analysis of the characteristics and nature of the population of a city, county, or other locality, but without at least an outline of facts about population the necessary framework for investigating and comprehending many other aspects of local life will be lacking.

Aside from determination of the beginning of a settlement and the actual size of its population over time, analysis of the composition of that population in terms of age, sex, ethnicity (and before 1865 freedom and slavery), and occupations will help to recreate the character of the community. In an area of any size – a county perhaps, or a large city – the spatial distribution and density of population, too, may call for investigation, bearing in mind that the social ingredients of population may vary within the territorial boundaries of the area being studied, and that, in particular, there are likely to be differences between rural and urban parts and between the nature of one part of a city and another.

The residential experience of different groups in large towns is also of interest. Did occupational, ethnic, or immigrant groups cluster together, and, if so, how did this affect the characteristics of a neighborhood?