History of the United States in a circle
Presidential Costs by Rachel Mercer offers a look at the history of the United States:
The outer circle illustrates presidential periods, the governing party, and whether or not the President died in office. The first inner circle shows the "eras" in history that those time periods covered. The third inner circle shows key foreign conflicts and wars. The fourth inner circle (purple) shows key legislative acts (or series of bills) that were issued. Finally, the bubbles in the middle indicate the average national debt, as indicated every 8 years.
I like the look, but the average debt numbers do seem kind of iffy. I could be wrong though.