Every subject can be studied backward in time because every event was caused by events that preceded it. A history research project can be made out of almost anything. Perhaps in the neighborhood where you grew up there was a very old building and you had always wondered about when it was built and what it was used for. Finding out what the neighborhood was like when that building was new can be an exciting search. An ideal topic is not only one about which you are curious but one about which you already know something.
Instructors are eager to help students who show a real interest in a topic.
Your instructor can assist you in selecting a subject related to your interests that also suits the particular course you are taking. A theme is more narrow than a topic. A theme is some important point about the topic that you wish to make. For the paper on King, you may want to show that his famous speech at the Lincoln Memorial in 1963 expressed several elements of his religious beliefs. In that case, your theme is the connection between the speech and King's earlier religious development.