Native American oppression, slavery in the U.S. and the women's suffrage movement are excellent topics for American history students. One of the most popular topics is the Civil War, either as a generalized subject or a look at individual battles or particular military leaders.
There are a wide variety of topics that are suitable for American history research papers. The Revolutionary War is of interest to many students of history, as is the exploration of America and the taming of the west. Notable events in American history are invariably good choices for research papers, such as the election of the country's first black president, the assassination of JFK or Lincoln or the impeachment of Nixon.