Clarissa “Clara” Harlowe Barton was an American Civil War nurse, humanitarian, and founder of the American Red Cross. Known as the “Angel of the Battlefield” for aiding soldiers at Antietam, Fredericksburg, and other battles, she later led efforts to locate missing soldiers and marked over 20,000 graves. In 1881 she founded and presided over the American Red Cross for 23 years, expanding its mission to disaster relief worldwide.

Source: Wikipedia

She assisted with the recovery after the 1889 Johnstown, Pennsylvania Flood and also spent a year helping people after the 1900 Galveston Hurricane in Galveston TX.