In God We Trust first appeared on the currency in 1864. Americans were
fighting the Civil War at that time, and perhaps the Union side wanted to
indicate that God favored the North. That horrible war is also when The Battle
Hymn of the Republic was first sung. It’s a beautiful but ominous hymn to a deity
envisioned as a God of War, a god who supports the righteous North. Many
secularists still disapprove of this motto. After all, the Bill of Rights does guarantee
separation of church and state.
We are a secular nation, and there is no place for such dogma as "In God We Trust" on our currency. The phenomenon is relatively recent and coincides generally with McCarthyism. Our nation is a secular one (note that there is not a single mention of a deity in our Constitution). We do not, and should not, "trust" in God. The slogan has no place on our currency.