Siple was born in Montpelier, Ohio on December 18, 1908, to Clyde Lavonius Siple and Fannie Hope Allman. His family moved to Erie, Pennsylvania, where he graduated from Central High School in 1926. He became an Eagle Scout in 1923 with 59 merit badges. After an extensive nationwide search in 1928, he was the first Eagle Scout selected for an Antarctic expedition, sailing with Richard E. Byrd on his ship the "City of New York". Siple appeared in the documentary film "With Byrd at the South Pole" (1930).