What years make up the 19th century? 20th century?

Although a number of things brought about world war one there was one even that push to europe over the edge. what was that event?

How did african americans the union during the civil war? a. by serving as representatives in congress b. by enlisting in the military to fight c. by organizing massive slave revolts in the south d. by negotiating for peace with the confederacy

Which type of constitutional power allows congress to regulate immigration and naturalization?