Research questions guide your research and analysis. These questions go beyond what can be answered by yes or no and surpass factual questions that can be easily answered with a statement of fact. Research questions should focus on how and why things happened. These questions will help you focus your research and develop your argument as you progress throughout your project.
From A Pocket Guide to Writing in History by Mary Lynn Rampolla:
"A meaningful historical question that calls for analysis and interpretation, and that might elicit some debate." (MLR p. 86)
This website also gives some really helpful ideas for writing research questions.
This is a great video on developing strong research questions.
Watch this video and follow along to map your ideas.