This is a video that shows a map of the United States, then highlights the state, and shows the date it entered into the Union. I use this to show my students how we spread from the east coast to the west coast. It is a great visual and can be used while you are teaching any point in U.S. History.
I use it while teaching about the 13 colonies and Manifest Destiny. If you teach any part of U.S. History when states are added this can be a helpful tool for you.