Last year we forked over about $1.9 trillion to Uncle Sam (who then spent $2.3 trillion). So where does all the money go? Lots of places, of course, but most of it goes to: 1. Department of Health and Human Services ($543 billion) 2. Social Security Administration ($530 billion) 3. Department of Defense ($437 billion) 4. Interest on Treasury debt ($321 billion) For more, go to page 5 of this pdf file.