These databases will allow you to search for journal literature and information from earlier coverage to the present. Secondary source content will allow you to find information in context and spans the environmental sciences, historical framework, political viewpoints, economic issues.
Issues and supporting documentation may be needed for demographics, population data, other census conditions or historical periods, social matters and different reference tools may be helpful. Data from Government Information, either US or International, GIS mapping, all establish relationships and context. Consult with librarians.