Why must the population be in the range of 640,000 and 650,000?
As of the 2000 U.S. census, 640,000-650,000 is the population range of typical Congressional districts in the United States. Population equality for each district ensures the “one person, one vote” guarantee in the Constitution. Note: If a state has fewer than 640,000 people, the people of that state still have one Congressional Representative, as guaranteed by the Constitution.