The Corpus of Historical American English (COHA) is the largest structured corpus of historical English. The corpus was created at Brigham Young University, with generous funding from the US National Endowment for the Humanities. It is also related toother large corpora of English that we have created or modified.
COHA allows you to quickly and easily search more than 400 million words of text of American English from 1810 to 2009. You can see how words, phrases and grammatical constructions have increased or decreased in frequency, how words have changed meaning over time, and how stylistic changes have taken place in the language. It’s a lot more than just frequency charts for individual words and phrases (like with Google Books / Culturomics) — although those types of searches can be done here as well, and yield essentially the same results as Google Books.