On this day in history - July 30th, 1956 - "In God We Trust" is adopted as the official motto of the United States.
The phrase was first used by Union troops as a battle cry at the Battle of Antietam. It appeared on coins on and off from 1873 until 1938, when it became mandatory.
During Dwight D. Eisenhower's administration in the middle of the Cold War, the Soviet Union advocated atheism for its citizens. The United States wanted to do something official to make its acknowledgement of a God known, so the 84th Congress passed a bill making "In God We Trust" official. Eisenhower signed it into law, and it was reaffirmed in 2006 by the Senate and in 2011 by the House of Representatives.