Commerce’s U.S. Census Bureau  reports that the U.S. population reached 314,395,013 at noon today—the 225th anniversary of the signing of the U.S. Constitution  on September 17, 1787, in Philadelphia. Twenty-five years ago, on the 200th anniversary, the population was 243,636,172. The very first census of 1790 counted 3,929,214 residents.
Today, September 17, is recognized as Constitution Day and Citizenship Day  to commemorate the creation and signing of the supreme law of the land and to honor and celebrate the privileges and responsibilities of U.S. citizenship for both native-born and naturalized citizens. The U.S. Constitution empowers the Congress to carry out the census in "such manner as they shall by Law direct" (Article I, Section 2). Read the Census in the Constitution .