Click on the History Reference Center link and select a time period from the "Timeline" box on the lower right-hand side of the page and click on the "search" button at the top of the screen. You will see a list of articles on topics from that time period. You could use this as a topic idea-generator.
America History & Life includes literature covering the history and culture of the United States and Canada, from prehistory to the present. The collection includes some 1,700 journal titles that are indexed selectively, 230 full text journals and 100 books. Click on the "CLIO" link in the upper left-hand corner of the page to see list of potential topics, then click on the timeline to see more detailed topic recommendations