In our secular age it has become popular to denigrate our national motto, "In God We Trust", as a merely modern fabrication chosen by Congress as recently as 1956. However, it's likely origin is much earlier and can be found in the final verse of our national anthem, The Star-Spangled Banner, penned in 1814 by Francis Scott Key.
O! thus be it ever, when freemen shall stand
Between their loved home and the war's desolation!
Blest with victory and peace, may the heav'n rescued land
Praise the Power that hath made and preserved us a nation.
Then conquer we must, when our cause it is just,
And this be our motto: 'In God is our trust.'
And the star-spangled banner in triumph shall wave
O'er the land of the free and the home of the brave!
Though I doubt you'd learn it or sing it in school.
(HT: SMI Blog.)