Originally Posted by Wiki page
In God We Trust is the official motto of the United States
Congress passed the Coinage Act (1864) on April 22, 1864. This legislation changed the composition of the one-cent coin and authorized the minting of the two-cent coin. The Mint Director was directed to develop the designs for these coins for final approval of the Secretary. In God We Trust first appeared on the 1864 two-cent coin.
According to a 2003 Gallup Poll, 90% of Americans approve of the inscription on U.S. coins.
The Supreme Court has upheld the motto because it has "lost through rote repetition any significant religious content". In such related decisions as Zorach v. Clauson, the Supreme Court has also held that the nation's "institutions presuppose a Supreme Being" and that government recognition of God does not constitute the establishment of such a state church as the Constitution's authors intended to prohibit.
So it is:
-Historically associated with the US' federal government for at least ~140 years, out of a total national history of around 230 years;
-The legal and official motto of the United States of America;
-Hugely popular with the American people;
-Upheld by your Supreme Court as not constituting a breach of your First Amendment.