Geographic keywords: Start with a specific geographic area as a keyword. Move to broader geographic areas as needed. (Example: "South Bend" > "St. Joseph County" > "Northern Indiana" > "Great Lakes region").
Gazetteers: Use a gazetteer to determine if the location or geographic feature you are searching has had a different name in the past. If so, include that name in your search. Gazetters can be found in the library collection or online.
Atlases: Add "atlas" as a keyword while searching the library catalog. Broad topics are usually better than narrow ones when searching for atlases (e.g., "food" or "agriculture", not "wheat" or "bananas"). Also keep in mind that atlases published more recently may contain reproductions of historical maps.
Online: Search online for maps produced by government agencies:
If you want a map published by the U.S. government, add [site:.gov] to the end of your search (e.g., [Canada map site:.gov]).
If you want a map published by another country's government, add the limiter for that government's top-level domain. For example, to find a map of India published by the government of Spain, search [India map site:.gob.es].
Think about agencies or organizations that may be interested in creating maps related to a particular topic (e.g., health topics) and search within that organization's website.
It is important to cite maps, just as you would cite any other resource you use in your work. The Citing Maps page from North Carolina State University Libraries provides examples for citing different types of cartographic materials.