Many, but not all, of the memorials you are researching will have an accompanying website created by the people, organization, or city government entity that sponsored the memorial and/or are responsible for maintaining it. These websites can be valuable primary sources! You can discover these websites by searching Google or following links in a Wikipedia entry, if one exists for the memorial you are researching.
Newspaper coverage of the memorials will help you find out more about local, national, and international contexts. For best results, you may want to search more than one newspaper database.