If you have any interest in the territorial growth of the United States, go over to Lincoln Mullen’s historical blog and check out his interactive map of American expansion. It is meticulous in its detail. You can activate a timeline with your mouse and roll over any particular territory for pertinent information. It is user friendly, and really engaging. I showed my 8 year old daughter the map, and she was mesmerized. We spent a half an hour playing with it the other evening.
Mullen has another interactive map of the expansion of slavery in the US from 1790-1860. Here is what he says about his methodology and purpose:
Using Census data available from the NHGIS, the visualization shows the population of slaves, of free African Americans, of all free people, and of the entire United States. It also shows those subjects as population densities and percentages of the population. For any given variable, the scales are held constant from year to year so that the user can see change over time. You can use the map for yourself, and I’ve also written briefly about what the map shows below. Historians have of course often made use of maps of slavery, in particular maps based on the Census, in support of their arguments. What I’ve tried to do in this interactive map is make it possible for users (including me) to explore the census data in support of making historical arguments.