The U.S. Census is the only comprehensive or "complete count" of the entire population of our country. It is the only source of data for ensuring everyone has a voice in Congress. "Representative democracy" is the cornerstone on which this nation was founded, and the census is the tool used by the federal government to preserve equal representation. The qualitative aspects of this representation has historically been, and is ever changing. Explore the history of the U.S. Census in this online exhibit.