In 1904, the U.S. hosted its first Olympics. It had a host of problems. But the event that was the most dangerous for athletes was the marathon.
Research:

Abbott, Karen. “The 1904 Olympic Marathon May Have Been the Strangest Ever.” Smithsonian. Aug. 7, 2012. https://www.smithsonianmag.com/history/the-1904-olympic-marathon-may-have-been-the-strangest-ever-14910747/
“Amateur Athletic Union Suspends Member for Life.” The Brunswick News. Sept. 4, 1904. https://www.newspapers.com/image/897913415/?terms=%22fred%20lorz%22%20&match=1
Britannica, The Editors of Encyclopaedia. "Russo-Japanese War". Encyclopedia Britannica, 17 May. 2023, https://www.britannica.com/event/Russo-Japanese-War
Britannica, The Editors of Encyclopaedia. "St. Louis 1904 Olympic Games". Encyclopedia Britannica, 24 Jun. 2023, https://www.britannica.com/event/St-Louis-1904-Olympic-Games
“Cuban Marathon Runner Carvajal Comes to Life.” The Evening World. April 11, 1907. https://www.newspapers.com/image/85305956/
“Felix Carvajal.” Olympics.com. https://olympics.com/en/athletes/felix-carvajal
Lawrence, Andrew. “Think the Tokyo Olympics are a bad idea? St Louis 1904 set the bar high.” The Guardian. July 13, 2021. https://www.theguardian.com/sport/2021/jul/13/st-louis-olympics-1904-tokyo-flawed-games
Longman, Jerry. “The Marathon’s Random Route to Its Length.” New York Times. April 20, 2012. https://www.nytimes.com/2012/04/21/sports/the-marathons-accidental-route-to-26-miles-385-yards.html?_r=0
Lucas, Charles J. P. “The Olympic Games 1904.” Woodward & Tiernan. 1905. Accessed online: https://library.olympics.com/Default/doc/SYRACUSE/29697/the-olympic-games-1904-by-charles-j-p-lucas?_lg=en-GB
“Olympic Games at St. Louis.” Weekly Democrat-News. Feb. 28, 1903. https://www.newspapers.com/image/954304418/?terms=olympic&match=1
Rodrigues, Ashwin. “The Unbelievable True Story of the Craziest Olympic Marathon.” Runners World. Aug. 6, 2021. https://www.runnersworld.com/runners-stories/a37039437/1904-olympic-marathon/
“William Garcia.” Olympics.com. https://olympics.com/en/athletes/william-garcia
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