It sounds like you're looking for a thesis statement or a topic to discuss in a paper. When discussing history, remember that there is still a lot of debate about timelines and order of events.
Travel is an interesting topic to write about. Over time, man has graduated from walking to riding animals to automobiles, airplanes, and ocean liners. There is a ton of information to draw from, so you might start with a quick overview of travel methods and then move to your historical topic.
For example, if you were writing about the methods armies have used to travel over the years, you would research infantry history, animal-drawn carts and carriages, and animals used as weapons, like elephants, which could also carry equipment. You would then move on to boats, which have been around for a long, long time, and move up from Viking Longboats to the ocean-sailing vessels used by England and Spain, and then to the first Ironclad ships in the 19th century, and then logically to modern diesel and nuclear-powered vessels. Finally, air travel would begin with balloons and airships, move through the Wright Brothers and the air battles of the First World War, and then to the role of air support in the Second World War and so forth.
Really, there is a lot of information to draw on. The most important thing to remember is to pick a topic you can write about clearly and logically, and support your arguments with facts. The standard essay form will serve you well here, introducing your topic and then the "research question" will be your Thesis statement. After that, lay out your points and facts in the Body, finish with a Conclusion that covers all your points simply, and Cite all your sources.