Zahm befriended 26th President of the United States Theodore Roosevelt, who also loved and read Dante in Italian. It was Father Zahm who talked President Roosevelt into participating in what came to be known as the Roosevelt-Rondon Scientific Expedition to South America, and which would also include Theodore's son, Kermit, and Colonel Da Silva Candido Rondon, to go up the "Rio da Dúvida" (River of Doubt, now the Roosevelt River). This trip deteriorated into a near disaster which caused one man to drown, another to be murdered, and Roosevelt nearly dying, shortening his life by probably ten years from the combined effects of malaria and infection. The trip almost cost the others their lives as well, as the members lost boats to waterfalls and rapids and almost ran out of food. They barely made it to the first sign of civilization and some certainty that they would survive. The elder Roosevelt had to be carried off his canoe, so weak and ravaged by sickness had he become.