Among all the other busyness on the one dollar bill — the serial numbers and seals, the ruffled outfit of George Washington, the elaborate crosshatching and filigree designed to foil counterfeiters — are four small words. In God We Trust.

The phrase first appeared on America's paper money on Oct. 1, 1957, one year after becoming the country's official motto. Now, a half century later, the motto is inspiring increased fervor and controversy, another skirmish in the battle over how America defines itself.

"The whole In God We Trust thing is much more layered than it first looks," says Charles C. Haynes, senior scholar at the First Amendment Center in Virginia.

On one side are those who argue that, especially as America becomes increasingly diverse, people of all faiths and no faith should be free from any official endorsement of religion.

On the other side are those who argue that the nation is at risk of being redefined as godless. For these people, Haynes says, there is a "new frontier" of efforts to make the national motto more prominent.

In Indiana, for example, a new license plate bearing the motto and an American flag has already been selected by over 1.3 million motorists since its debut earlier this year, according to the Indiana Bureau of Motor Vehicles. The American Civil Liberties Union of Indiana has filed a lawsuit challenging the law that lets drivers buy the plates without having to fork over extra money for what the ACLU argues is a specialty plate (The state argues that it's a standard plate.) The ACLU also complains that the extra money to print the In God We Trust plates (about 50 cents more per plate — over $650,000 so far) has come out of the Indiana Highway Fund — state money for what the ACLU believes is a religious message.

It's no coincidence that new venues for the motto are popping up at a time of anxiety in America, Haynes says, because national anxiety has jump-started every "In God We Trust" effort in the country's history.

"The first use was at a time of our greatest national crisis, the Civil War," he says, "because, for many people, the Civil War was God's judgment on America. And it revived the old anxiety that, because the Constitution didn't formally acknowledge God, we would suffer." This angst resulted, at first, in an effort to add God and Christ to the preamble, and when that didn't work, supporters persuaded the Secretary of the Treasury in 1864 to put "In God We Trust" on the 2-cent coin.

Nearly a century later, in the early years of the Cold War, Congress voted to make "In God We Trust" the national motto (replacing the original motto, "E pluribus unum" — "Out of many, one") and voted, in 1957, to engrave it on all U.S. currency. It was a way to symbolically say that Americans, unlike Communists, aren't godless, Haynes says, and "that we will triumph not because of us but because of our dependence on almighty God."