|Olympic medal record|
|Representing the United States|
Forshaw ran the Marathon in three Olympic Games. He competed for the United States in the 1908 Summer Olympics held in London, Great Britain where he won the bronze medal in the Marathon . At the 1906 Intercalated Games in Athens he finished in twelfth place, and at the 1912 Summer Olympics in Stockholm he was 10th in the event.
On May 6, 1905, Forshaw beat Sidney Hatch and Felix Carvajol to win the Missouri Athletic Club's All-Western Marathon in a time of 3:15:58. Three years later on May 2, 1908, he finished second to Hatch in the same race in 2:30:01, his best time in the event. In both races, Forshaw competed for the Missouri Athletic Club.
In March, 1912, Forshaw was one of "twenty of the best distance runners in the middle west" scheduled to participate in a 20-mile indoor marathon at Riverview Rink in Chicago, Illinois. He also finished second to Joseph Erxleben in the 25-mile Missouri Athletic Club marathon in St. Louis on May 4, 1912 to earn a spot on the United States Olympic Team.
Forshaw entered in the Missouri Athletic Club's All-Western Marathon six times between 1905 and 1912. In addition to winning in the inaugural event he came second three times and fourth twice. He reportedly finished every race in which he ever ran. After retiring from distance running he twice served as President of the Western Amateur Athletic Union.
17 years later after his death his grandson would marry the daughter of Phyllis Schlafly
- "Joseph Forshaw". Olympedia. Retrieved 8 March 2021.
- Sullivan, J.E., ed. (January 1910). "Marathon Road Races". Spalding's Official Athletic Almanac for 1910. XII. New York: American Sports Publishing Co. p. 91. Retrieved April 28, 2012.
- "They've Revived It: We Thought the Marathon Game Was Dead and Buried but Not Yet". The Milwaukee Journal. Milwaukee. March 8, 1912. p. 13. Retrieved April 29, 2012.
- Martin, David E.; Gynn, Roger W.H. (2000). "1912: A South African Success Spree in Stockholm". The Olympic Marathon. Champaign, Illinois: Human Kinetics Publishers. p. 82. ISBN 9780880119696. Retrieved April 29, 2012.
- USA Track & Field (2004). "2004 USA Olympic Team Trials: Men's Marathon Media Guide Supplement" (PDF). Santa Barbara, California: USA Track & Field. p. 7. Retrieved April 29, 2012.
- O'Shaughnessy, Christine Forshaw (May 2004). "Joseph Forshaw, Marathon Runner" (PDF). Journal of Olympic History. 12 (2): 10–19. Retrieved May 2, 2016.