This site is very easy to navigate because each map is depicted as a large thumbnail which is titled with the topic of the map. When the user clicks to Enter each map, they are presented with an overview of the topic and how it fits into history.
Next, they will view four brief pieces of information that will help them to read the map and find pertinent information or just explore. For example, The Overland Trails 1840-1860:
1. "map traces the routes of about two dozen migrants over the three trails."
2. "Read a migrant’s diary and follow their journey on the map."
3. "Use the timeline to select a year and see the pace of migration west from Missouri (86°W) to the west coast (123°W)."
4. "Use the flow map to see how the number of people migrating west changed, sometimes enormously, from year to year."
The site is easy to use and includes an introduction on the use of various elements such as overlays. The maps include icons that are easy to decipher for use. For example, when using and overlay there is are plus/minus buttons to zoom in/out as well as a slider to lighten or darken the overlay.