Find the historical population figures for your community for the 20th century. Create a chart by ten-year intervals. Determine the most rapid periods of growth, and try to discover what caused them. (One source of the necessary population numbers is the U.S. Census home page, www.census.gov. Look in the right-hand column in Data Finders to find QuickFacts, and select your state and county. At the top of the large table of current information that appears select your county or city. Then click on "Browse more datasets and look down the page for the heading "Historical Population Counts.")