The Penguin operation in America was started in 1939, four years after the successful launch of Penguin in Britain. The collection retained the green colour code for crime Fiction books which had characterised the British covers since the 1935 publication of Penguin no. 5 (the first crime published in the collection,  Dorothy L Sayers’s The Unpleasantness at the Bellona Club). But the American market was not prepared for the sobriety of the non illustrated British covers. The  illustrations make the American covers instantly recognisable.