Creating a research map is a great way to start interacting with your topic of inquiry.
Creating the Research Map will help you paint the landscape of the information resources for your topic: primary/secondary sources; contemporary/historical; US/international; thematic/subject specific, etc. Knowing the type of sources you may need will help you identify the most relevant search tools (databases).
See Christine's example of a Research Map for history of Tokyo project.
Historical dictionaries, published bibliographies, atlases are all good starting place. To locate these sources in library catalogs, you can use some of the following strategies: