The “Peace Sign” was created on February 21, 1958 by British graphic designer and Christian pacifist Gerald Holtom. Holtom was tasked with creating the banners and signs for a nuclear disarmament march in London, and he wanted a visual that would stick in the public’s mind.
The peace symbol debuted on April 4, 1958, Easter weekend that year, at a rally of the Direct Action Committee Against Nuclear War, which included a march from London to Aldermaston. The marchers carried 500 of Holtom's peace symbols on sticks, with half of the signs black on a white background and the other half white on a green background. In Britain, the symbol became the emblem for the Campaign for Nuclear Disarmament, thus causing the design to become synonymous with that Cold War cause. Holtom was a conscientious objector during World War II and thus a likely supporter of its message. 
The design is, in part, modeled after naval semaphore flags that sailors use to communicate. Holtom combined the codes for “N” (two flags angled down at 45 degrees) for “nuclear” and “D” (one flag pointed straight up and one flag pointed straight down) for “disarmament.”
Holtom never copyrighted his design for the peace symbol intentionally, so anyone in the world can use it for any purpose, in any medium, for free.