A well-read friend, GHF, sent me a link to an American civic literacy quiz; he scored 58 out of 60 (I told you he was well-read!). I just finished taking it; even though I recently reviewed U.S. history to Reconstruction, I got a miserable (by homeschool standards :D) 45/60, or 75%. Keep in mind that the vast majority of American college students aren't doing too well either.
Take it for yourself; review beforehand if you want; but no peeking during the test! Comment with your score too; see if you can beat the college graduates.
Update 11/22/08: I took it again; this time it has 33 questions, out of which I answered 29 correctly = 87.88%. A significant improvement. :) November's average was about 77%.