I will expand on this in the sessions to come, but try your hand at
Finding maps and data: Here are some resources to work with: https://delicious.com/tchammond/TLT394,dataSources. If you want country-level data, GapMinder.org is a particularly rich source. I can't imagine there's a better one-stop shop, particularly for historical info.
If you want to make life easy for yourself, just limit yourself to census data: https://delicious.com/tchammond/TLT394,dataSources,census. The Historical Census Browser from the University of Virginia, for example, is particularly easy to work with.
Keep in mind that you can satisfy the next assignment's requirement simply by playing with data -- you don't necessarily need to come up with an entirely new map. Just put new data on an old map, mash it around, and you're good. Depending on your topic, though, you may want to hunt down a new map or modify an existing map using the "Analyze" tab in My World.