At the end of March 2010, the national debt stood at $12.8 trillion. And if you look at some of the U.S. debt clocks that display real-time estimates, such as this one here, you will see that in the three months since that number has exceeded $13 trillion — and counting. What is commonly referred to as ”the U.S. debt” is basically securities such as savings bonds, bills, notes and other bonds that are issued by the Treasury and other federal agencies under special financing authorities. If you own Treasuries (or a fund that invests in them), you own a piece of the national debt. Who else does? The latest numbers can be found in the latest Treasury Bulletin, released in June 2010 and reflecting data through March 31, 2010. The largest chunk of Treasury securities is, in fact, held by Federal Reserve banks, adding up to $940 billion at the end of the period. And when it comes to foreign holders, number one is China, which at that time held nearly $900 billion’s worth. (Japan was a close second, with $784.9 billion.) You can find the details in the Treasury Bulletin – or for a more visual presentation, check out our infographic.