I happened to watch Cromwell recently. The movie depicts the events surrounding Cromwell who led pro-Parliament forces against the King, eventually resulting in trying the king for treason and beheading him (Ooops, spoiler alert). Within the movie is a scene where the Puritans are protesting, and among the messages scrawled on the signs was "In God We Trust". I'm betting that was historically accurate.
And it was not put on the paper bills until that time. FFRF has a raffle at each convention asking people to trade in their dirty money for some clean money and one can buy a stamp (I did) to stamp over the In god we trust with in Reason we trust.
Almost got it - it's out of many, one. I have no clue how to fix a meme otherwise I'd of sent this to my religious friend.
And under the Supreme Court case with a link listed below, that motto should be unconstitutional.
[mtsu.edu]