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---most American Jews came from Eastern Europe, and this is a folk custom which originated there. It has no basis in any religious beliefs aside from the importance of remembering our loved ones who have died. We are supposed to visit the graves of our deceased relatives on the anniversary of their deaths and around certain holy seasons. It still means a lot to some people to go there and see that others have visited. The stones that we leave behind are a visible token that this soul has not been forgotten. It is not a religious requirement to do this.