Historical maps provide one way of illustrating such changes.
To get a sense of how such changes are illustrated on maps, I suggest looking at an atlas of world history. Good examples are The Times Atlas of World History and The Times Concise Atlas of World History , both of which exist in various editions. Specific historical atlases for particular regions of the world or particular countries also exist. The library has a number of historical atlases. You choose the subject you'd like to show and the time period that would be most useful for the comparison.