Edmonds' interest in adventure was sparked by Maturin Murray Ballou's book "Fanny Campbell, the Female Pirate Captain"', telling the story of Fanny Campbell and her adventures on a pirate ship during the American Revolution while dressed as a man. Campbell continued dressing as a man after the war in order to pursue other adventures, to which Edmonds attributed her desire to cross dress. She enlisted in Company F of the 2nd Michigan Infantry on May 25, 1861, also known as the Flint Union Greys. On her second try, she disguised herself as a man named Franklin Flint Thompson, the middle name possibly after the city of Flint, Michigan where she volunteered. She felt that it was her duty to serve the United States, as it was her new country. She at first served as a field nurse, participating in several campaigns under General McClellan, including the First and Second Battle of Bull Run, Antietam, the Peninsula Campaign, Vicksburg, Fredericksburg, and others. However, some historians claim that these reports place her in more than one location at the same time.