After the end of hostilities, he trained as a barrel organ builder with the French company Limonaire Frères, in the Black Forest town of Waldkirch.
Almost from the start of its foundation, De Kleist built contacts in the United States, and commuted regularly across the Atlantic Ocean.
After the United States Government announced the imposition of import tariffs from 1893 on new organs, he was pursued by Allan Herschell, to persuade him to set up in business in the United States, and hence supply the various fairground ride manufacturers with locally made European quality barrel organs.
Having been voted in previously as president of the Common Council of North Tonawanda, in November 1906 he was elected Mayor of the city for a term of two years.
After his term as mayor ended, and suffering from ill health, De Kleist retired with his wife Charlotte (née Chelius) to Berlin in 1911, dying in Biarritz, France in 1913 from a heart attack.