This lovely video explains the origins of the World War II Keep Calm and Carry On poster that was rediscovered in 2000 and turned into a meme around 2009:
You can see images of the other two posters in the series here: They read “Freedom Is In Peril. Defend It With All Your Might” and “Your Courage, Your Cheerfulness, Your Resolution Will Bring Us Victory.”
The “Keep Calm and…” genre has gotten ridiculous. For the love of god, people aren’t even trying to match the typeface anymore. If you must, Avenir and Gill Sans are pretty close matches, and one dude made a Keep Calm typeface that even includes the little crown. You can get a replica Keep Calm and Carry On poster from Barter Books here.