Answer:
In God We Trust was added to the Latin saying E pluribus unum ("Out of many") in 1956 through a declaration by Congress.
The background to this decision was the Cold War and an effort to underscore the unity of the American people against the "godless communists". The declaration was initiated by the Dixiecrat and Congress member Charles E. Bennett, a member of the inner leadership circle of the anti-communist Christian fundamentalist network International Christian Leadership (ICL), which strives for a nation based on Christian principles.