All-Time Record Currently Sits at $231.68 Billion
Of the ten largest monthly deficits that the United States has posted since 1980 (which is as far back as our data goes), all occurred after the start of 2008.
Does this surprise you? After all, the financial health of the United States went from decent to truly awful in just a few short months thanks to the "Great Recession". It seems like eons ago when the United States was actually posting surpluses (the last annual surplus, which clocked in at $127.3 billion, was posted back in 2001).

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So, how bad have the monthly deficits gotten since the start of the "Great Recession" in December of 2007?
Let's take a look - here are the ten largest monthly deficits for the United States since October of 1980:
1. $231.7 billion (February 2012)
2. $222.5 billion (February 2011)
3. $220.9 billion (February 2010)
4. $198.2 billion (March 2012)
5. $193.8 billion (February 2009)
6. $191.6 billion (March 2009)
7. $189.6 billion (May 2009)
8. $188.1 billion (March 2011)
9. $180.7 billion (July 2009)
10. $176.3 billion (October 2009)
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In case you were curious - the largest surplus posted in any single month came in April of 2001, when the United States posted a monthly surplus of $189.8 billion.
Source: Deficit History in the United States