In 1864, Congress passed the Coinage Act so that adaptations could be made to U.S. currency, and on April 22, "IN GOD WE TRUST" was first printed on the two-cent coin.
At least part of the motivation for adding the motto to America's currency was to acknowledge increased religious sentiment that had flourished during the Civil War. The war had torn apart the country and the Federal government used the addition to show solidarity and a common unification.
However, Theodore Roosevelt took issue with the motto, considering its usage "dangerously close to sacrilege." Still, it remained for decades. In fact, the omission of the slogan on the 1907 Indian Head eagle coin caused public outrage and prompted Congress to pass a bill mandating its inclusion on all coins.
During the Cold War era, the U.S. government tried to distinguish itself from the Soviet Union, which promoted state-sponsored atheism. The 84th Congress of 1956 passed a joint resolution "declaring IN GOD WE TRUST the national motto of the United States."
"In God We Trust" appeared on all American currency after 1956.
A minting error in 2007 resulted in some Presidential $1 coins minted without the motto–these are known as "godless dollars." Over the years, people have sought to challenge the motto on U.S. currency, taking offense at its religious tone. Courts have consistently ruled that the motto is secular, and no longer has any “theological or ritualistic impact," though many scholars disagree.
A 2003 joint poll stated that 90% of Americans support the inscription "In God We Trust" on U.S. coins. The motto remains on all U.S. currency today.