American soldier who fought, disguised as a man, in the Civil War.

Sarah Edmonson received scant education as a child, and sometime in the 1850s she ran away from home. For a time she was an itinerant seller of Bibles, dressing as a man and using the name Frank Thompson. She gradually made her way west and by 1861 had established residence in Flint, Michigan. Shortly after the outbreak of the American Civil War, she enlisted—as Frank Thompson—in a volunteer infantry company in Flint that became Company F, 2nd Michigan Infantry. Her disguise was a complete success for nearly a year. She took part in the Battle of Blackburn's Ford, the First Battle of Bull Run (Bull Run, battles of), and the Peninsular Campaign of April–July 1862. At Fredericksburg, December 13, 1862, she was an aide to Colonel Orlando M. Poe. At least twice she undertook intelligence missions behind Confederate lines “disguised” as a woman. She accompanied the 2nd Michigan to Kentucky early in 1863 and, for reasons that are unclear, deserted in April.

Taking the name Sarah Edmonds, she worked as a nurse for the United States Christian Commission. In 1865 she published a lurid and very popular fictional account of her experiences as Nurse and Spy in the Union Army. She married in 1867 and thereafter moved often—to Michigan, Illinois, Ohio, Louisiana, and Kansas. In 1882, living then in Fort Scott, Kansas, she began securing affidavits from old army comrades in order to apply for a veteran's pension, and in July 1884 the pension was granted by Congress to “Sarah E.E. Seelye 【her married name】, alias Frank Thompson.” In Houston, Texas, a short time before her death, she became the only woman to be mustered into the Grand Army of the Republic as a regular member.