Brigham Young's Mark Davies has just made available, in alpha, a new Corpus of Historical American English. If you don't know about Mark's free corpora, you should check them all out.
He's (almost?) singlehandedly put together the largest collection of freely useable corpora. Of the above, only the BNC was not compiled at Brigham Young.
Also, when I pointed out to him that it would be lovely if we could query the range of publications and documents in which a text appears, he agreed and it should be possible in a few months.