Biggest Holders of US Debt Is Not China or Japan But..

As the US government spends an unprecedented amount of money to fix the nation's economy, there is an equally great need to raise the cash to pay for it. This is accomplished through borrowing, whereby Uncle Sam sells Treasury securities of varying maturity.
For investors, the government bills, notes and bonds are considered a safe financial product because they have a guaranteed rate of return, based on faith in future US tax revenues. The government has been partially funding operations via Treasury securities for decades.
This borrowing adds to the national debt, which has climbed above $11 trillion and is rising every day. Much of that debt is held by private sector, but about 40 percent is held by public entities, including parts of the government.  Here's who owns the most. 
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1. Federal Reserve and US Intragovernmental Holdings
That’s right, the biggest holder of US government debt is actually inside the United States. The Federal Reserve system of banks and other US intragovernmental holdings account for a stunning $5.127 trillion in US Treasury debt. This is the most recent number available (Sept 2009), and is at an all-time high, rising in every reporting period since 2007. About a decade ago, the total government holdings were "only" $2.5 trillion.
Slideshow Here..