Pierce, B.W. Portland, Oregon. 1890. Library of Congress Geography & Map Division (PM 724). Bird's Eye Views. By John W. Reps. New York: Princeton Architectural Press. 114. Cropped Reproduction of Lithograph.
It can be a challenge to settle on a topic. You aren't going to know whether you've hit upon an appropriate topic until you've done a little research and found out what has already been published on that and similar topics. Do some searching for books, articles, and websites in order to begin getting a sense of things - think of this as a "scan" of the literature. Your understanding of your topic will evolve over time, and your thesis may change accordingly.
The literature can give you a good sense of whether you have hit upon a topic at the right level of specificity. If you find tons of information, you've probably got too broad a topic at the moment. Narrow your topic down - for example, you may choose to focus on a particular location, time period, or aspect of your topic.
In contrast, if you find very little information, this could mean that your search vocabulary is not quite right (contact me for assistance with this), or that you've hit upon a topic that hasn't been extensively studied yet. Broaden your topic out a little until you find closely related research that will help inform your work. Remember, even if you hit upon a completely unique research topic, you still need to put the topic into its context by reviewing related published research!
Once you've honed in on your thesis topic, it is time to do a full-fledged literature search. This is more comprehensive than the "scan" process you went through to get a better understanding of the topic. Browse the tabs of this guide for links to the wide variety of search tools available to you in order to conduct your literature search.