On this day in 1956, President Dwight D. Eisenhower signed a law officially declaring "In God We Trust" to be the nation's official motto (there was no national motto prior). The law, P.L. 84-140, also mandated that the phrase be printed on all American paper currency. The phrase had been placed on U.S. coins since the Civil War and the Secretary of the Treasury, George Humphrey, suggested adding the phrase to paper currency as well.
This occurred two years after Eisenhower amended the Pledge of Allegiance to include the phrase "under God".
Of note, one possible origin of the phrase "In God We Trust" comes from Francis Scott Key, the man who wrote the poem that would become the National Anthem. Written in 1814, the final stanza contains the phrase:"...And this be our motto: 'In God is our trust'."
The arguments supporting and opposing the phrase are varied. Consider the following:
President Eisenhower wrote, "In this way we are reaffirming the transcendence of religious faith in America's heritage and future. . ."
The 84th United States Congress had required that the words appear on all currency, as a Cold War measure; a sort of religious safety valve. "It is proper to remind all of us of this self-evident truth--that as long as this country trusts in God, it will prevail."
President Theodore Roosevelt took issue with placing the motto on coinage as he considered it sacrilegious to put the name of God on money. Roosevelt wrote, "it seems to me eminently unwise to cheapen such a motto by use on coins, just as it would be to cheapen it by use on postage stamps, or in advertisements."
The "Establishment Clause of the First Amendment" states that Congress shall make no law respecting an establishment of religion. Critics contend that the motto's placement on money constitutes the "establishment" of a religion by the government. However, the Supreme Court has upheld the motto because it has "lost through rote repetition any significant religious content".
The first paper money with the phrase "In God We Trust" was not printed until 1957.
The argument over the appropriateness of that motto has been raging ever since.