On July 27, 1759, the French mathematician and philosopher Pierre Louis Moreau de Maupertuis died in Basel, where he had retreated in his later years. He is remembered for his principle of least action and his expedition to Lapland, which confirmed the Earth’s oblate shape. On the same date in 1855, a cholera outbreak began in Basel, fueled by poor hygiene and contaminated drinking water; by October 6, 399 people had fallen ill and 205 had died.