The definitive collection in the US for peace and political records, posters,
photographs, etc. is the Swarthmore College Peace Collection. Also, Haverford
College Library holds the archives for the American Friends Service Committee
and some other Quaker-related peace & justice groups. In the late 1970's I
was the staff person for a short-lived and not particularly successful
solidarity
organization and I was delighted to discover that Swarthmore wanted all the
remains that would otherwise have haunted all my moves, several boxes worth
of minutes, ads, correspondence, posters, buttons, position papers, magazines,
etc.