A primary source refers to a text, video, or audio that was there for the event. For the presidential election of 2004, you could use a speech from any of the candidates as a primary source. This would help the people you are presenting to understand the views/beliefs of the candidates.
Yes, most Northerners were anti-slavery.
The main cause of WW1 was the assassination of the Archduke Franz Ferdinand of Austria-Hungary. The other causes are Militarism, Alliances, Nationalism, and Imperialism.
