The original national motto: "E Pluribus Unum"
The original motto of the United States was secular. "E Pluribus Unum" is Latin for "One from many" or "One from many parts." It refers to the welding of a single federal state from a group of individual political units -- originally colonies and now states.
On 1776-JUL-4, Congress appointed John Adams, Benjamin Franklin, and Thomas Jefferson to prepare a design for the Great Seal of the United States. The first design, submitted to Congress on 1776-AUG-10 used the motto "E Pluribus Unum." It was rejected. Five other designs also failed to meet with Congress' approval during the next five years. In 1782, Congress asked Mr. Thomson, Secretary of Congress, to complete the project. Thomson, along with a friend named Barton, produced a design that was accepted by Congress on 1782-JUN-10. It included an eagle with a heart-shaped shield, holding arrows and an olive branch in its claws. The motto "E Pluribus Unum" appeared on a scroll held in its beak. The seal was first used on 1782-SEP-16. It was first used on some federal coins in 1795.
The replacement motto: "In God We Trust:"
Almost a century and a half ago, 11 Protestant denominations mounted a campaign to add references to God to the U.S. Constitution and other federal documents. Rev. M.R. Watkinson of Ridleyville PA was the first of many to write a letter to the Secretary of the Treasury Salmon P. Chase in 1861 to promote this concept. Watkinson suggested the words "God, Liberty, Law." In 1863, Chase asked the Director of the Mint, James Pollock to prepare suitable wording for a motto to be used on Union coins used during the Civil War. Pollock suggested "Our Trust Is In God," "Our God And Our Country," "God And Our Country," and "God Our Trust." Chase picked to have "In God We Trust" used on some of the coins. The phrase was a subtle reminder that the Union was on the side of God regarding slavery. Congress passed legislation. Since a 1837 Act of Congress specified the mottos and devices that were to be placed on U.S. coins, it was necessary to pass another Act to enable the motto to be added. This was done on 1886-APR-22. "The motto has been in continuous use on the one-cent coin since 1909, and on the ten-cent coin since 1916. It also has appeared on all gold coins and silver dollar coins, half-dollar coins, and quarter-dollar coins struck since" 1908-JUL-1.
Decades later, Theodore Roosevelt disapproved of the motto. In a letter to William Boldly on 1907-NOV-11, he wrote: "My own feeling in the matter is due to my very firm conviction that to put such a motto on coins, or to use it in any kindred manner, not only does no good but does positive harm, and is in effect irreverence, which comes dangerously close to sacrilege...It is a motto which it is indeed well to have inscribed on our great national monuments, in our temples of justice, in our legislative halls, and in building such as those at West Point and Annapolis -- in short, wherever it will tend to arouse and inspire a lofty emotion in those who look thereon. But 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."
In 1956, the nation was suffering through the height of the cold war, and the McCarthy communist witch hunt. Partly in reaction to these factors, the 84th Congress passed a joint resolution to replace the existing motto with "In God we Trust." The president signed the resolution into law on 1956-JUL-30. The change was partly motivated by a desire to differentiate between communism, which promotes Atheism, and Western capitalistic democracies, which were at least nominally Christian. The phrase "Atheistic Communists" has been repeated so many times that the public has linked Atheism with communism; the two are often considered synonymous. Many consider Atheism as unpatriotic and "un-American" as is communism. The new motto was first used on paper money in 1957, when it was added to the one-dollar silver certificate. By 1966, "In God we Trust" was added to all paper money, from $1 to $100 denominations.