Conversation so far:
when was in god we trust put on coins
The Congress passed the Act of April 22, 1864 and IN GOD WE TRUST first appeared on the 1864 two cent coin.
when was the motto in god we trust placed on paper currency
IN GOD WE TRUST was first used on paper money in 1957, when it appeared on the one-dollar silver certificate.
when did the paper currency bearing the motto in god we trust enter circulation
The first paper currency bearing the motto IN GOD WE TRUST entered circulation on October 1, 1957.

Question: when was the motto declared a national motto
Self-contained rewrite: when was the motto in god we trust declared a national motto