May 5, 1818 – Karl Marx, author of the Communist Manifesto, is born in Trier, Prussia, Germany.
May 6, 1856 – Psychoanalysis founder Sigmund Freund is born in Pribor, Austria (now Czech Republic).
May 6, 1856 – American Arctic explorer Rear Admiral Robert E. Peary is born in Cresson, Pennsylvania.
May 8, 1884 – 33rd President of the United States Harry S. Truman is born in Lamar, Missouri.