Consider using a gazetteer
A gazetteer is a place name dictionary or index used to search the history of a place. This is particularly helpful for learning about places whose names or boundaries have changed over time or for names with variant spellings. If a place name has changed over time, you can incorporate its other names in your search. You can search OneSearch with the name of the country or region you are interested in and the word "gazetteer" or "place names."
National and International data:
The Map library has a wealth of historic maps all the way up through contemporary maps. They have aerial photographs of Colorado from multiple decades up through the present. They have maps of international cities, but specialize in Colorado. Contact firstname.lastname@example.org to set up a research appointment to find print maps.
To cite a map or aerial photograph, use the same basic style guidelines as you use to cite your books and articles (for example: MLA, APA, or Chicago Manual of Style). However, maps/aerial photographs have some unusual elements, such as scale, that should be included.
Dartmouth College Library has an excellent guide on citing cartographic resources.