Loomis went to school in Evanston until 1914. Upon meeting his future Oregon High School teammate Sherman Landers, he transferred to Oregon, Illinois to continue training with him. Together, they began a rise that would take them to the 1920 Olympic Games. Although Frank Loomis was an AAU champion in 220 yd (200 m) hurdles in 1917 and 1918 and in 440 yd (400 m) hurdles in 1920, the main favourite in Antwerpen was John Norton, who had run a new world record of 54.2 just two months before the Olympics. Despite that, Loomis won the 400 m hurdles final easily in a new world record of 54.0, beating Norton to second place by 0.6 seconds.
Landers-Loomis Field in Oregon, Illinois is named partially in his honor.