Encyclopedias attempt to summarize the state of knowledge in a field of inquiry. A good encyclopedia can be a valuable starting point for your research.
Two online reference collections that students often find useful are: Oxford Reference Online, and Gale Virtual Reference Library.
Below is a list of major, recently-published sources. In general, to find historical atlases, a good approach is to search in the Online Catalog using the subject terms "historical geography". For example:
Or try subject words "history" and "maps". For example:
Not all of the books retrieved will be atlases, but many will be and most at least will include maps.