Postcards of Clara Barton, 1904, undated

Clara Barton was born in North Oxford, Massachusetts, in 1821, the daughter of Stephen and Sarah Stone Barton. Her father was a member of the local government and the militia. She had four siblings, Sarah, Stephen, Dorothea, and David. Barton was very shy in her youth and her parents encouraged her to become a teacher, in hopes that this would ease her shyness. She began teaching in 1838 or 1839, working in schools in Oxford and North Oxford, Massachusetts. She left teaching in 1851 to attend the Clinton Liberal Institute in New York. In 1852 she established New Jersey's first free school in Bordentown, although she was not permitted to serve as the school's principal, as the school board felt it was an unsuitable job for a woman. She was given the position of "female assistant" and the uncongenial work environment led her to have a nervous breakdown.

In 1855, she moved to Washington, DC and began work as a clerk in the United States Patent Office, receiving the same salary as her male co-workers. Due to political opposition to women holding jobs in the government, she was demoted to the position of copyist and in 1858 she was fired. She returned to the patent office after the election of Abraham Lincoln. The Baltimore Riot of April 19, 1861, led to the first bloodshed of the Civil War and the beginning of Barton's nursing career; she nursed forty men who had been wounded in the riot and began providing clothing and other supplies to men in uniform. In August 1862, she received permission to work on the front lines and gained a number of supporters who provided supplies. She worked in field hospitals near several battlefields, including Cedar Mountain, Second Bull Run, Antietam, and Fredericksburg, helping both Union and Confederate soldiers. After the war, Barton managed the Office of Missing Soldiers, with the mission of locating and identifying soldiers killed or missing in action. Barton and her assistants responded to thousands of inquiries and helped locate over 20,000 missing men. Her office also found and properly buried over 20,000 Union soldiers who had been buried in unmarked graves.

After the war, Barton lectured about her experiences, gaining wide recognition. She met Susan B. Anthony and Frederick Douglass and became involved in the suffrage and civil rights movements. In 1868, suffering from exhaustion, she traveled to Europe. The following year, she met Louis Appia, secretary and founding member of the International Committee for Relief to Wounded Soldiers (later the International Committee of the Red Cross). She continued her nursing work while in Europe, assisting in the preparation of military hospitals at the beginning of the Franco-Prussian War in 1871 and working with the Red Cross throughout the war. In 1871 she was put in charge of distributing supplies to people in need in Paris.

After her return to the United States, Barton began work to establish an American branch of the Red Cross, and to secure the government's support for it. In 1878, she met with President Rutherford B. Hayes, who disputed the need for such a society. She ultimately persuaded President Chester Arthur that there was need for the organization in the event of earthquakes or other natural disasters, as well as in times of war. The first official meeting of the American branch was held in May 1881, with Barton as president and the first local society was held later that year. The society's activities included aiding survivors of floods of the Ohio river in 1884 and providing supplies to residents of Texas during the 1887 famine there. In 1896 Barton and other members of the American Red Cross also assisted in humanitarian efforts in Cuba and the Ottoman empire. During the Spanish-American War in 1898, the society assisted refugees and prisoners of war. In 1900, Barton conducted her final field operation for the American Red Cross, providing aid to victims of a hurricane in Galveston, Texas, and establishing an orphanage there.

Criticism of Barton's leadership style, which some saw as egocentric, arose during the Progressive Era (1896-1916). Factions developed within the organization and she was forced to resign in 1904, partially due to a controversy concerning her handling of financial resources. After resigning, Barton established the National First Aid Society. She published her autobiography, The Story of My Childhood, in 1908. Barton died of pneumonia in 1912.