Where is the official clock of the US?

Answer 1

Original answer: I believe that the US Naval Observatory is the official time keeper of the United States.

The rest of the story: The USNO is one half of the equation. The National Institute of Standards and Technology is the other half.

Answer 2

The official clock of the United States is located at the U.S. Naval Observatory in Washington, D.C. It is known as the Master Clock and serves as the primary time standard for the U.S. government.