Legally mandated by the Constitution of the United States, our government conducts censuses every ten years on years ending in zero. Traditionally the census takers went from house to house with a questionnaire. Although questions varied from decade to decade the main questions remained the same (name and general demographics). A specific "census date" was selected for each year, and households were to supply information on every person living in (or expected to be living in) their residence on that specific date. This assigned census date allowed census takers to capture a coherent "snapshot" and avoid double counting.
A comprehensive treasury of American genealogical sources—rich in unique primary sources, local and family histories, and finding aids.
